The former Rotherham striker had tweeted earlier on Monday that he was “off for a medical” and the 28-year-old has now completed a switch to Molineux.
Wanderers have the option to make the deal permanent at the end of the campaign.
Both clubs announced the deal on Monday evening, with Wolves’ head of football development and recruitment Kevin Thelwell saying: “We are really pleased to bring Adam to the club.
“He has a proven goalscoring pedigree with a terrific strike rate in both the Championship and the Premier League.
“We have been chasing him for a long time and are delighted that he is now a Wolves player.”
A Cardiff statement added: “The loan runs until 31st May 2016, inclusive. Adam is ineligble to feature in either of our fixtures with Wolves during the 2015/16 season.
“We’d like to thank Adam for his contribution and wish him luck for the future.”
Le Fondre was out of favour at the Bluebirds after joining from Reading in 2014, scoring just three times in 25 games, and spent time on loan at Bolton last season, netting eight goals in 17 outings.
Wolves boss Kenny Jackett has been searching for a new striker after losing Bakary Sako and failing to land Chris Wood, who joined Leeds.
The head coach only has Benik Afobe and Nouha Dicko as his frontline strikers and needed fresh firepower.