The 25-year-old scored on his full debut against Benetton Treviso and grabbed a memorable brace - including a stunning 87th minute try - against Connacht in March.
Tuculet has now decided to return home to Argentina to represent his country's Super Rugby team - that will be based in Buenos Aires - and signed until at least the end of the 2018 Super Rugby season.
"I know I have three matches left with Cardiff Blues and would like to thank the fans for the support and hope that we can have a great end to the season," he said.
Billy Millard, Head of Elite Performance at Cardiff Blues, added: "Joaquin has been a real success since he moved to Cardiff Blues with his performances on the field and character off it and I know the players and fans will be sad to see him go.
"However, the chance to play Super Rugby in Argentina and continue his international career are obviously big pulls for Joaquin and so he will leave at the end of the season with our very best wishes.
"Joaquin has missed the last few games for Cardiff Blues through injury but he is now keen to make a playing return in the closing weeks of the GUINNESS PRO12 season and continue to leave a lasting memory with our fans."
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