Bentley looked to be heading out of the exit door at White Hart Lane after failing to secure a regular first-team place.
The England winger had a much-publicised falling out with Redknapp in a training ground match back in December and has hardly featured since.
But with Aaron Lennon and Niko Kranjcar both ruled out of the game, Redknapp made a bold move to recall Bentley and it paid off as the former Blackburn midfielder scored the crucial second to help Tottenham record their first victory of 2010.
Fulham never looked like getting something out of the game and they have now gone 29 games without a victory in a London derby away from home.
The home side could have broken the deadlock inside the opening 60 seconds when Tom Huddlestone's shot from the edge of the box produced a superb save from Mark Schwarzer diving low to his right.
Former Tottenham striker Bobby Zamora almost made a dream return to the Fulham starting line-up on 11 minutes when he latched onto a pass from Zoltan Gera and saw his shot well-saved by Heurelho Gomes.
But it was Tottenham who opened the scoring on 27 minutes. Schwarzer failed to deal with a high cross in from Bentley, Luka Modric refused to let the ball go out of play and crossed back in for Peter Crouch who flicked the ball over the Fulham keeper.
Modric looked back to his best on the left-hand side of Tottenham's midfield and could have doubled their lead on the stroke of half-time.
The Croatian midfielder produced a superb piece of skill inside the box and saw his shot fall inches over the bar.
Tottenham continued to mount pressure on the Fulham goal and came close again on 50 minutes when Bentley's cross picked out Wilson Palacios whose close-range header flew just over the bar.
The home side sealed all three points with the crucial second on the hour mark and it was an extra special moment for Bentley who clearly had a point to prove on his return to the side.
Gareth Bale was fouled on the edge of the box, Bentley saw his free-kick take a wicked deflection off Bjorn Helge Riise and the ball flew past Schwarzer into the corner of the net.