After leaving the Camp Nou last season, the Ghanaian returned to the Serie A with Fiorentina although regular game time was not on the cards.
As a result, the 32-year-old joined the Turkish on the final day of transfer window in a loan deal.
"If I have to be honest, I spoke to Besiktas two years ago," Boateng said on the Official Besiktas YouTube Channel.
"I always wanted to come and play in Tukey because I grew up with all my Turkish friends in Berlin and they were all Besiktas supporters.
"As soon as the news came out everybody texted me and they said finally you went home.
"There was not a lot of thinking because when I heard Besiktas, I told my agent please make the deal I want to go and play for this great club."