Fulham substitute Collins John levelled within a minute of being brought on to deny Derby in a tense FA Cup clash.
The Rams had taken the lead through another substitute, Marcus Tudgay, who swept in Tommy Smith's left-wing cross from close range on 56 minutes.
Fulham initially struggled to respond but 50 seconds after replacing Tomasz Radzinski, John latched on to Mark Pembridge's long ball and fired home.
Derby continued to press but Fulham held on to take the tie to a replay.
Chris Coleman's side have not lost in any competition since 28 December but they were without key trio Papa Bouba Diop, Zesh Rehman and Carlos Bocanegra at Pride Park.
The Premiership side made a cagey start to the game, but slowly imposed themselves on the match.
Derby winger Marco Reich was the only man to really trouble the visitors' defence in the first half, but neither Smith or Grzegorz Rasiak could get on the end of his deliveries from the left-flank.
Fulham's first real chance came on 25 minutes when Lee Clark and Radzinski linked up to send Sylvain Legwinski clear, but his shot flew high and wide.
Andy Cole also should have done better with a free header from a Radzinski cross, failing to connect properly when in yards of space.
The Rams were being outplayed in the closing stages of the first half but they came out strongly after the break.
First Inigo Idiakez whipped in a teasing cross which just evaded Rasiak at the far post, then Tudgay headed over from Smith's centre.
A goal by the home side looked likely and it arrived on 56 minutes.
Smith and Rasiak linked up well on the right and from Smith's cross Tudgay - who had replaced the injured Reich at half-time - finished expertly from close range.
Fulham continued to look vulnerable and Smith went close again with a rasping drive from outside the box on 62 minutes. But the game turned on Coleman's decision to replace Radzinski with John with 20 minutes left.
The decision paid instant dividends as Pembridge's long ball over the top missed Andrew Cole but fell for John who smashed home from close range.
Derby almost went back in front immediately - only the outstretched leg of Van der Dar stopping Tudgay from making it 2-1.
The Cottagers still had some defending to be done, but Derby could not find a way through in the closing stages and the two sides will meet again next month.
Derby boss George Burley:
"It was a cracking game in the second half - both sides wanted to win it but I am a little disappointed not to be through.
"All credit to Fulham, they fought back well to equalise.
"But we kept going and almost got a winner. I couldn't have asked any more of my players."
Fulham boss Chris Coleman:
"I'm delighted. Derby are a very good team and in good form. They played with a lot of confidence.
"The pitch wasn't great so it was very difficult for us to play our normal football but we battled away.
"We have got them back to Craven Cottage and hopefully we can finish them off there."
Derby: Camp, Kenna, Johnson, Huddlestone, Mills, Bisgaard, Idiakez, Taylor, Reich (Tudgay 45), Rasiak, Smith.
Subs Not Used: Grant, Junior, Bolder, Boertien.
Goals: Tudgay 56.
Fulham: Van der Sar, Volz, Goma, Knight, Rosenior, Legwinski, Clark, Pembridge, Radzinski (John 70), Boa Morte, Cole.
Subs Not Used: Crossley, McBride, Jensen, Pearce.
Goals: John 71.
Ref: G Poll (Hertfordshire).