Le Fondre has been top scorer in each of his three seasons at the Madejski Stadium, and becomes the third striker to join Ole Gunnar Solskjaer's ranks since relegation from the Premier League.
Federico Macheda and Javi Guerra have already moved to the Cardiff City Stadium, joining the likes of Fraizer Campbell, Kenwyne Jones and Nicky Maynard in south Wales.
The 27-year-old is unfazed by the competition for places, though, and expressed his delight at linking up former Manchester United hitman Solskjaer.
"It’s such a great opportunity for me to come here to Cardiff City and play for a boyhood hero of mine in Ole Gunnar Solskjaer," Le Fondre told the club's official website.
"It was a move I just couldn't say no to.
"I'm delighted to be working with Ole and I can't wait to get started. Scoring is what I'm about, I’ve often got into double figures during my career although looking back at last season it's one I really wanted to score more in personally.
"They are the high standards I set myself and now the aim is to do that with Cardiff City."
