Anthony Stewart scored for Wycombe in the fifth minute of stoppage time to deny managerless Portsmouth their first League Two win in seven matches.
Matt McClure put Wycombe ahead with a low shot before Pompey's David Connolly had a penalty saved by Matt Ingram after he had been fouled by Sam Wood.
Portsmouth did level when Andy Barcham fired high into the net and went ahead through Patrick Agyemang's header.
But with seconds left, Wycombe salvaged a point when Stewart headed in.
It was a rearranged game after
October's meeting was abandoned at half-time
with the score level at 1-1 because of a waterlogged pitch.
VIEW FROM THE DRESSING ROOM
Wycombe manager Gareth Ainsworth told BBC Three Counties Radio:
"I've got mixed feelings. I'm elated we got the draw but I'm angry that we played like we did in the second half.
"Once the ball came on the floor in the first half I thought we had the better of the play.
"They camped out in our half second half. I was disappointed because the decisions we made in the middle of the park weren't right
"We had a plan to alleviate the pressure and it didn't work. But thank goodness for the penalty save and Anthony's late header at the end is fantastic.
"It's about time I had a bit of luck and a late goal."
Portsmouth 40 Carson 04 East (N'Gala - 38' ) 33 Potts 13 Ertl (Agyemang - 78' ) 05 Devera 06 Bradley 35 Wallace Booked (Connolly - 45' ) 20 Cooper Booked 18 Bird 11 Holmes 07 Barcham Substitutes 03 N'Gala 08 Padovani 09 Connolly 14 Painter 16 Ferry 23 Agyemang 25 Sullivan Wycombe Wanderers 01 Ingram Booked 02 McCoy 11 Wood 09 Spring Booked 06 Johnson Booked (Stewart - 81' ) 30 Doherty 08 Lewis 12 Cowan-Hall 29 McClure 07 Morgan (Kuffour - 87' ) 28 Knott Booked (Kretzschmar - 87' ) Substitutes 03 Dunne 05 Stewart 13 Horlock 18 Kuffour 20 Craig 22 Kretzschmar 23 Arnold
Ref: Darren Drysdale