Kanu (left) is congratulated after scoring the winner
By Les Roopanarine
Portsmouth substitute Kanu capped a flurry of late drama with a last-gasp winner to deny Iain Dowie a point in his first match as Hull manager.
Caleb Folan drew first blood for Hull when he redirected Craig Fagan's long-range effort from six yards.
Tommy Smith equalised from close range, but Folan struck on the counter with 17 minutes left to restore Hull's lead.
Pompey looked doomed, but Jamie O'Hara bent in a late free-kick and Kanu swept in a Nadir Belhadj cross at the death.
On another day the spotlight would have fallen squarely on Dowie in his first game in charge since replacing the sacked Phil Brown.
But in keeping with the surreal nature of Pompey's season it was the hosts who stole the limelight as they demonstrated their commitment to the Premier League cause despite confirmation this week of a nine-point penalty for going into administration.
Grant had hinted that he might field a weakened side in protest at the points deduction that all but consigns Pompey to the Championship next season.
Pompey stength of character pleases Grant
He made five changes to the side beaten 4-1 at Liverpool on Monday night, but the return of David James in goal - and the inclusion of other key performers such as O'Hara and Frederic Picquionne - ensured no one would mistake Pompey's teamsheet for a white flag.
That was just as well, because for much of the afternoon Hull looked odds-on to improve an abysmal away record that has seen them fail to win on their league travels for 12 months.
Dowie's side should have taken an early lead when Kevin Kilbane floated a far-post cross to Jan Vennegoor of Hesselink, whose angled header beat James only to trickle back off the post.
The lurking Folan failed to react on that occasion, but when Fagan fired goalwards after Pompey had cleared a Jimmy Bullard corner, his afternoon took a somewhat fortuitous turn for the better, the ball flying in off his shin after taking a deflection off Marc Wilson.
It was a deserved lead for Hull, for whom Bullard had been increasingly influential as the visitors took control in midfield, but Dowie was understandably more preoccupied with events at the opposite end of the pitch.
He spent much of the game barking orders at his back four, and for a time his imprecations seemed to be having the desired effect.
But the visitors' newfound defensive cohesion was undone nine minutes from the break when Hreiddarson knock the ball back across goal from a corner, allowing Smith to prod home his first goal since his summer move from Watford.
It was a spirited response from Pompey, but Dowie's decision to introduce Richard Garcia with 20 minutes remaining looked to have reaped dividends when the Australian's pace on the counter-attack set up Folan to angle a low effort across James and into the far corner.
Hull defeat hurts new boss Dowie
Hull appeared to be on their way to a victory that would reinvigorate their faltering campaign but with three minutes left Bullard conceded a free-kick on the edge of the area which O'Hara curled brilliantly beyond Boaz Myhill and into the top corner.
Hull were still reeling when Kanu, boldly sent on as a 57th-minute replacement for Aaron Mokoena, swept home a Belhadj cut-back to snatch all three points for his side.
Portsmouth manager Avram Grant: "It's always good to win, especially after a difficult week, and it's always good to be positive.
"It's going to take a lot for us to stay in the league, but we've spoken a lot about character, spirit and mentality.
"Anything can happen in football, right up to the last moment, and we showed that today."
Hull manager Iain Dowie: "It was bitterly disappointing, because with three minutes to go you think you're going to see it over the line.
"It showed how cruel this league is, but I think we showed spirit and determination.
"Portsmouth are playing with abandon and we just didn't keep the ball well enough."
90:00+5:05 The game is over, as the referee blows his whistle.
88:46 Assist on the goal came from Nadir Belhadj.
88:46 GOAL - Nwankwo Kanu:Portsmouth 3 - 2 Hull Nwankwo Kanu fires in a goal from close in low into the middle of the goal. Portsmouth 3-2 Hull.
87:41 GOAL - Jamie O'Hara:Portsmouth 2 - 2 Hull Jamie O'Hara hits the back of the net with a goal direct from the free kick from just outside the box to the top left corner
of the goal. Portsmouth 2-2 Hull.
86:54 Marc Wilson fouled by Jimmy Bullard, the ref awards a free kick.
85:41 Shot on goal by Danny Webber from just inside the area clears the crossbar.
85:28 Marc Wilson fouled by Caleb Folan, the ref awards a free kick. Free kick taken by Nadir Belhadj.
84:54 Tommy Smith takes a shot. Blocked by Frederic Piquionne.
83:57 Substitution Ricardo Rocha goes off and Angelos Basinas comes on.
83:48 Handball decision goes against Craig Fagan. Indirect free kick taken by David James.
83:07 Hayden Mullins gives away a free kick for an unfair challenge on Craig Fagan. Boaz Myhill restarts play with the free kick.
82:18 Booking Boaz Myhill receives a yellow card for time wasting.
81:42 Danny Webber is ruled offside. Boaz Myhill takes the indirect free kick.
81:05 Substitution Danny Webber comes on in place of Quincy Owusu-Abeyie.
78:32 Free kick awarded for a foul by Nick Barmby on Nwankwo Kanu. Quincy Owusu-Abeyie fires a strike on goal direct from the free
76:46 A cross is delivered by Quincy Owusu-Abeyie, save by Boaz Myhill.
75:40 Richard Garcia crosses the ball, save by David James.
75:01 Frederic Piquionne concedes a free kick for a foul on Bernard Mendy. Boaz Myhill takes the free kick.
72:42 Assist on the goal came from Richard Garcia. Foul by Steven Mouyokolo on Nwankwo Kanu, free kick awarded. Shot comes in from
Marc Wilson from the free kick.
72:42 GOAL - Caleb Folan:Portsmouth 1 - 2 Hull Caleb Folan grabs a goal from close in to the bottom left corner of the goal. Portsmouth 1-2 Hull.
71:11 The official flags Caleb Folan offside. Jamie O'Hara takes the direct free kick.
69:43 Substitution Richard Garcia joins the action as a substitute, replacing Andy Dawson.
65:17 Substitution Nick Barmby joins the action as a substitute, replacing Jan Vennegoor of Hesselink.
65:04 Shot from long distance by Jamie O'Hara goes wide of the left-hand upright.
64:58 The ball is delivered by Nadir Belhadj, Paul McShane makes a clearance.
63:10 Short corner worked by Jamie O'Hara. Quincy Owusu-Abeyie delivers the ball, clearance made by Bernard Mendy.
Correction - 62:20 Tommy Smith takes a shot. Paul McShane gets a block in. Quincy Owusu-Abeyie decides to take the corner short.
62:20 Tommy Smith takes a shot. Blocked by Paul McShane. Quincy Owusu-Abeyie decides to take a short corner.
61:44 The ball is crossed by Dean Marney, clearance made by Ricardo Rocha.
60:52 Tommy Smith challenges Andy Dawson unfairly and gives away a free kick. Andy Dawson takes the indirect free kick.
60:03 Foul by Jan Vennegoor of Hesselink on Marc Wilson, free kick awarded. Nadir Belhadj restarts play with the free kick.
59:05 Marc Wilson concedes a free kick for a foul on Jimmy Bullard. Jimmy Bullard restarts play with the free kick.
58:01 The ball is swung over by Quincy Owusu-Abeyie, Boaz Myhill makes a save.
57:40 Hayden Mullins delivers the ball.
56:52 Tommy Smith sends in a cross, save made by Boaz Myhill.
55:50 Indirect free kick taken by David James.
55:50 Substitution Nwankwo Kanu on for Aaron Mokoena.
55:50 The assistant referee flags for offside against Caleb Folan.
55:08 Jimmy Bullard delivers the ball.
54:26 A cross is delivered by Kevin Kilbane.
54:19 The ball is swung over by Bernard Mendy, Aaron Mokoena manages to make a clearance.
53:15 Nadir Belhadj delivers the ball, save made by Boaz Myhill.
52:36 The ball is sent over by Nadir Belhadj, clearance by Andy Dawson. Short corner taken by Jamie O'Hara from the right by-line.
Ricardo Rocha produces a cross, Jan Vennegoor of Hesselink manages to make a clearance.
49:11 Shot from long range by Craig Fagan goes wide of the left-hand post.
48:33 The ball is delivered by Quincy Owusu-Abeyie, clearance made by Andy Dawson.
46:45 The ball is delivered by Tommy Smith, Boaz Myhill makes a save.
46:06 Nadir Belhadj produces a cross.
45:58 The ball is swung over by Nadir Belhadj, Craig Fagan gets a block in.
45:22 The assistant referee flags for offside against Jan Vennegoor of Hesselink. David James takes the indirect free kick.
45:01 The second half kicks off.
45:00+2:01 The referee blows for half time.
45:00+0:54 Kevin Kilbane delivers the ball.
44:01 Craig Fagan crosses the ball, clearance made by Ricardo Rocha.
42:52 Dean Marney produces a right-footed shot from the edge of the box and misses to the right of the goal.
41:30 Jamie O'Hara takes a short corner. Jamie O'Hara takes a shot. Boaz Myhill makes a save.
40:37 A cross is delivered by Jamie O'Hara, Paul McShane manages to make a clearance. Jamie O'Hara decides to take the corner short.
Jamie O'Hara takes a short corner. The ball is swung over by Quincy Owusu-Abeyie, Craig Fagan gets a block in.
40:21 Quincy Owusu-Abeyie sends in a cross.
39:45 The offside flag is raised against Caleb Folan. Hermann Hreidarsson restarts play with the free kick.
36:43 GOAL - Tommy Smith:Portsmouth 1 - 1 Hull Goal scored by Tommy Smith from close range low into the middle of the goal. Portsmouth 1-1 Hull.
36:26 Short corner worked by Jamie O'Hara. Jamie O'Hara produces a cross,
35:56 Jamie O'Hara delivers the ball, Tommy Smith takes a shot. Andy Dawson gets a block in.
32:21 Jimmy Bullard delivers the ball from the free kick right-footed from left wing, Caleb Folan gets a block in.
32:21 Booking Booking for David James for unsporting behaviour.
31:58 David James challenges Caleb Folan unfairly and gives away a free kick.
31:11 Nadir Belhadj has an effort at goal from outside the box which misses left.
30:57 Short corner taken by Jamie O'Hara.
29:54 Paul McShane challenges Quincy Owusu-Abeyie unfairly and gives away a free kick. Jamie O'Hara has an effort direct from the
free kick, Jan Vennegoor of Hesselink gets a block in.
Correction - 26:38 GOAL - Caleb Folan:Portsmouth 0 - 1 Hull Caleb Folan gets on the score sheet with a goal from close range low into the middle of the goal. Portsmouth 0-1 Hull.
26:38 Blocked by Caleb Folan. Assist on the goal came from Craig Fagan.
26:38 GOAL - Craig Fagan:Portsmouth 0 - 1 Hull Goal scored by Craig Fagan from just outside the box low into the middle of the goal. Portsmouth 0-1 Hull.
Correction - 25:57 Jimmy Bullard takes a shot. Blocked by Aaron Mokoena. Corner taken right-footed by Jimmy Bullard to the near post, Frederic
Piquionne manages to make a clearance. Craig Fagan takes a shot.
25:57 Jimmy Bullard takes a shot. Blocked by Aaron Mokoena. Corner taken right-footed by Jimmy Bullard from the right by-line to
the near post, clearance made by Frederic Piquionne.
24:54 Jimmy Bullard produces a right-footed shot from long distance which goes wide right of the goal.
21:55 Tommy Smith takes a shot. Blocked by Bernard Mendy. Short corner worked by Quincy Owusu-Abeyie. Effort from the edge of the
area by Nadir Belhadj goes wide of the left-hand post.
21:35 The ball is swung over by Craig Fagan, clearance made by Hermann Hreidarsson.
18:51 Quincy Owusu-Abeyie produces a right-footed shot from just outside the box that misses to the right of the net.
18:00 Foul by Caleb Folan on Ricardo Rocha, free kick awarded. Free kick taken by David James.
16:21 The ball is crossed by Quincy Owusu-Abeyie.
13:02 Free kick awarded for a foul by Jamie O'Hara on Craig Fagan. Boaz Myhill restarts play with the free kick.
10:20 Jamie O'Hara produces a left-footed effort from long distance that goes harmlessly over the bar.
9:15 Jamie O'Hara decides to take the corner short. The ball is crossed by Jamie O'Hara, clearance by Bernard Mendy.
8:23 Quincy Owusu-Abeyie decides to take the corner short.
6:40 Free kick awarded for an unfair challenge on Quincy Owusu-Abeyie by Bernard Mendy. Marc Wilson has an effort direct from the
3:25 Dean Marney takes a shot. Blocked by Hayden Mullins. The ball is crossed by Kevin Kilbane, Headed effort from the edge of
the area by Jan Vennegoor of Hesselink strikes the post.
3:18 Bernard Mendy delivers the ball.
2:27 The ball is swung over by Jamie O'Hara, clearance made by Steven Mouyokolo.
0:58 Free kick awarded for an unfair challenge on Bernard Mendy by Marc Wilson. Free kick taken by Boaz Myhill.
0:00 The game kicks-off.
Live text and data provided by The Press Association.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.