The Spaniard has swapped the Premier League for the Bundesliga on loan for the remainder of the season, with no mention of an option to buy.
Mainz confirmed that Bojan would begin training with the squad on Monday morning.
Malli replacement to make his mark?
The versatile forward will be hoping to hit the ground running in his fifth different country, having previously played for Barcelona, Roma, Ajax and AC Mian as well as Stoke.
Having fallen out of favour with Mark Hughes, this is the perfect chance to show the Potters just what they're missing.
Despite having a sizeable amount of experience behind him, the Spaniard is still just 26 and has plenty to look forward to in the coming months especially.
Bojan will most likely be the man that takes over from Yunus Malli in the attacking midfield role, with the attacking midfielder moving to VfL Wolfsburg earlier this month.
Schröder, Schmidt and Bojan have their say
Rouven Schröder credited the Spaniard as "a player with an outstanding career path", as well as confirming "the sporting and economic conditions were good enough to excite him and win him over". The club's sporting director added, "Bojan wants to fill the current gap. We're happy about the quality of the sport."
Martin Schmidt, the Mainz head coach, was pleased to have got his man: "In Bojan we got a player who is dangerous in front of goal and creative." He continued, "I'm looking forward to the challenge of integrating him into the team over the coming months. "
Bojan admitted his excitement with the move, "For me it's an honor. I'm looking forward to seeing the team as well as the fans and be able to help the Zerofivers on the pitch."