The Swiss frontman spent last season on loan at former club Bayer Leverkusen, scoring one goal in 18 league appearances - though 14 of those were from the bench.
And it was confirmed by Hoffenheim on Monday that the 25-year-old was on his way to Kasimpasa, who finished sixth in the Super Lig, for an undisclosed fee.
Derdiyok began his career with Old Boys in his homeland, before signing for Swiss giants Basel in 2006.
A move to Leverkusen followed in 2009, but he was offloaded to Hoffenheim after scoring 25 goals in 90 Bundesliga appearances.
He failed to hold down a first-team spot at the Rhein-Neckar Arena before his temporary departure last year, and has not been named as part of his country's squad for the 2014 FIFA World Cup, despite possessing more caps than the rest of the selected strikers combined.
