City signed the 24-year-old for a club-record fee of £5.3 million to bring him to Ashton Gate. Eclipsing the sides transfer record previously held by fellow African, Ivorian international Jonathan Kodjia who signed for £3.25 million in 2015 also from Angers.
"I think he's going to be a huge player for us," head coach Lee Johnson told the side’s website.
"He fits the bill for us because he’ll complement all of our strikers perfectly. He’s powerful, he’s quick and I think he’s got the potential to get even bigger and stronger physically."
The former Clermont forward scored nine times in 36 appearances last season.
A number of undisclosed English teams have been following the Saint-Louis born attacker according to bristolpost.co.uk and representatives from different English teams have been to Stade Raymond Kopa to watch him.
Diedhiou will be expected to fill the void left by Chelsea loanee Tammy Abraham. The striker who scored 26 goals in all competitions for them last season is now expected to move to Premier League club Swansea City.