Powerful Number Eight Vosawai has put pen to paper on a contract that will see him move to Blues from RaboDirect PRO12 rivals Benetton Treviso this summer.
The exciting Fijian-born back row, who has won 14 caps for Italy, becomes the latest recruit ahead of next season.
Blues have also signed New Zealand international lock forward Jarrad Hoeata, Exeter prop Craig Mitchell, Scarlets flanker Josh Turnbull, Gloucester scrum half Tavis Knoyle, Bristol wing George Watkins and Dragons back row Ieuan Jones.
Vosawai, who stands a menacing 6ft 2in and weighs 17st 5lbs, is a dynamic and destructive ball carrier and featured for Italy in the 6 Nations clash against Ireland at Lansdowne Road in March this year.
The 30-year-old made his Azzurri debut in the 2007 World Cup warm-up clash against Japan and later featured in three games in the showpiece tournament, starting the pool game with Portugal.
Vosawai said: "First of all I would like to thank God for my life and the many blessings in it. Secondly I would like to thank Benetton Treviso for the last four years of my career.
"Treviso have been there for me through thick and thin, and have nurtured me into the rugby player I am today. I will miss being part of the family in Treviso and Benetton rugby.
"Now there's a new page in my life and I am grateful that Richard Holland and his team has given me the opportunity to be part of the Cardiff Blues family.
"Cardiff are a top side with rich heritage and tradition in rugby and I know that they will bring out the best in me. It is an exciting time for me and I'm looking forward to putting on the Blues jersey next season at the Arms Park."
Chief Executive Richard Holland added: "We are delighted to be in a position to now confirm, after much speculation, that Manoa will join the Blues next season. He is the latest addition to the exciting squad we are building for next year and beyond.
"Manoa is keen to make a huge impression in Wales and we would like to thank the WRU for its support over this signing. We will now complete the visa process as we prepare to welcome Manoa to Blues in the coming months."