Leon Johnson's 96th-minute header salvaged a 1-1 draw for 10-man Wycombe and denied Scunthorpe a place in the automatic promotion places at Adams Park.
Former Jamaica international Deon Burton's first goal in 12 matches appeared to hand the Iron their fourth straight win, but the Chairboys struck at the death to pinch a valuable point.
Wycombe, without a win in their previous seven league games, started the brighter and had the first opportunity when Matt McClure's effort rolled agonisingly wide.
Sam Wood then fired straight at Scunthorpe stopper Sam Slocombe from inside the area moments later but the Iron grew into the game and David Syers' drive forced Matt Ingram into a fine low save.
On 49 minutes, 37-year-old Burton broke the deadlock with a smart finish from 12 yards and Wycombe were in trouble when Josh Scowen was sent off after two late tackles in the space of five minutes after the break.
Ingram kept the hosts in it, though, denying Sam Winnall and keeping out Syers' header before Johnson sent the home fans into raptures deep into injury time.