Iniesta joined Barcelona as a 12-year-old, and has won 31 major trophies during his time with the Catalan giants.
The 33-year-old held a special press conference on Friday afternoon to announce his exit, although the Spain international refused to name his next club.
"This is my last season at Barcelona. This was a decision which took a lot of thought. Barcelona are the best club in the world and they have given me everything," a visibly emotional Iniesta told reporters.
"This club deserves the best version of me and in the near future I will not be able to give that. It is best for me to leave this club feeling important, still winning titles.
"It is very difficult for me to say these words but I am so thankful to everyone at Barca and La Masia who made me who I am. I will always carry Barcelona in my heart. I want to thank everyone who has been with me in the bad times and the good.
"There are things to talk about and to finalise. I always said I would never compete against my club. At the end of the season I will communicate the place I have chosen."
Iniesta has scored twice and provided three assists in 39 appearances for Barcelona this season, and could add another La Liga title to his trophy collection this weekend.