James Beattie's injury-time penalty opened Southampton's account and eased the pressure on manager Paul Sturrock.
Southampton came from 2-1 down to level through Anders Svensson's thumping equaliser after Kevin Phillips had fired them into an early lead.
Blackburn equalised soon after the restart through Barry Ferguson's fine finish from the edge of the area.
Paul Dickov then struck from close-range to give Rovers the advantage which they failed to hold.
Southampton carved out the first semblance of a chance, seven minutes into a tentative start by both sides, Graeme Le Saux's curled cross just eluding Fabrice Fernandes and Phillips.
But Tugay took advantage of David Prutton's slip to drive forward and slide a pass to Jonathan Stead whose powerful drive brought a full-length save from Antti Niemi.
James Beattie had been very subdued but on 13 minutes Craig Short's poor defensive header popped the ball up for the England striker whose snapshot from 25 yards drifted a yard wide.
Svensson's screamer levelled to set up a dramatic finale
Stead then took advantage of some nervous Southampton defending but his sight of goal was quickly closed down by Claus Lundekvam's block.
Space was at a premium in a congested midfield but Blackburn found width when Gary Flitcroft's pass got Brett Emerton in behind the Southampton defence, only for the Australian's cross to lack conviction and allow Lundekvam to clear.
Le Saux whipped in a free-kick and Beattie won the second ball only to plant his header straight at Friedel.
But it was a temporary reprieve as Southampton took advantage of some poor Blackburn defending to sweep into the lead on 31 minutes.
Fernandes appeared to have dwelled on the ball too long but his patience was rewarded as his cross found Phillips who lost his statuesque marker Emerton to control the ball and drill his 150th league goal past Friedel.
The goal perked up Southampton's confidence and after Anders Svensson fired a weak shot at Friedel from 18 yards, the Swede's cross was met by Beattie at the far post but his header lacked power to trouble the Blackburn keeper.
Blackburn boss Graeme Souness replaced Dwight Yorke and Gary Flitcroft with Paul Dickov and Lucas Neil at half-time and within four minutes it paid dividends as Dickov set up Ferguson to fire in from 16 yards off the inside of Niemi's left-hand post.
Southampton's fragile confidence evaporated and Stead latched on to a poor clearance to drill a shot inches wide as Blackburn began to grow in authority.
Phillips looked the best player on display and he showed great skill in working space to release Beattie whose route was blocked by Johansson.Southampton enjoyed a good spell of pressure but were dealt a body blow as Blackburn took the lead on 68 minutes.
Emerton chased down a lost cause and clipped over a cross for Dickov to control and fire past Niemi.
Southampton showed good spirit though and after Friedel denied Phillips from point-blank range, they drew level on 74 minutes with a sublime goal from Svensson.
Beattie slipped Michael Gray on the right touchline and whipped in a cross that begged for a touch. Le Saux retrieved it and laid the ball into the path of Svensson who lashed a first-time shot past Friedel.
Niemi then reacted superbly to deny Dickov who was again frustrated in a manic goalmouth scramble as Beattie desperately cleared.
A frantic finish had a dramatic twist when referee Andy D'Urso spotted an injury-time push by Short on Beattie.
The Saints striker, linked with a move to Aston Villa, kept a cool head to fire his penalty past Friedel.
Southampton: Niemi, Telfer, Lundekvam, Higginbotham, Le Saux,
Fernandes, Delap, Prutton, Anders Svensson, Beattie, Phillips.
Subs Not Used: Crouch, Cranie, Best, Van Damme, Smith.
Goals: Phillips 32, Anders Svensson 74, Beattie 90 pen.
Blackburn: Friedel, Emerton, Short, Johansson,
Gray (Gresko 89), Flitcroft (Neill 45), Ferguson, Tugay,
Matteo, Yorke (Dickov 45), Stead.
Subs Not Used: Enckelman, De Pedro.
Booked: Dickov, Ferguson, Johansson.
Goals: Ferguson 50, Dickov 68.
Ref: A D'Urso (Essex).