Rendell featured in just 13 matches for Posh but had successful loan spells at Cambridge United and Torquay.
Chairboys boss Gary Waddock told the club's website: "He's a proven goalscorer at this level, and above."
Rendell spent the whole of last season on loan at Torquay scoring 12 league goals in 35 starts.
Waddock said: "He had a successful loan period at Torquay last season and found the net on a regular basis.
"I'm confident with the way we play and the amount of chances we create he will score here."
Source: BBC Sport
