The 25-year-old utility back has arrived from Grenoble on an initial deal until the end of the season.
Tuculet joins countryman Lucas Amorosino at Blues and will link up with the region after Argentina’s test against France next weekend.
The dynamic back has played a total of 19 games for his country – most recently last Friday as Argentina defeated Italy in Genoa – since making his international debut in 2012.
Tuculet has started at full back in both Argentina’s tour matches this autumn, against Scotland and Italy, and has scored a total of six international tries.
The Puma – who has had playing spells at Sale Sharks, Grenoble and Bordeaux Begles – also featured for the Barbarians against Australia at Twickenham earlier this month.
Director of Rugby Mark Hammett said: “Joaquin is a quality international player who will add to the squad we are building here at Cardiff Blues. We all look forward to his arrival in the coming weeks.
“Joaquin is strong under the high ball, has a strong left footed kicking game and is also very good at offloading in the tackle.
“His versatility gives us real options in the back line and with the recent injury to Rhys Patchell his signing also comes at the right time for us.”
Tuculet said: “I spoke with my international team-mate and friend Lucas Amorosino and he told me all about the passion of the supporters and the quality of the staff and the players and so I did not hesitate when making the decision to join the region.
“I’m looking forward to meeting my new team-mates and the coaching staff. I know I will be working with a very talented and ambitious group and so I am determined to have a strong season and I hope to show the Cardiff Blues supporters my best rugby.”
