Inter announced the signing of the player this afternoon. Candreva spent four seasons at Lazio, making over 200 appearances.
Candreva expressed his delight at the move and also thanked his former club.
"I'm really proud and happy to be here," he told the club's website.
"I always wanted to move to Inter and it is a very strong emotion to have arrived at Inter.
"I thank Lazio for the seasons we spent together and for giving me the chance to achieve this dream.
"Now I cannot wait to play at San Siro and feel the warmth of the Inter fans".