The 29-year-old joins the Nerazzurri from fellow Serie A side Lazio, signing a four year deal with Roberto Mancini's men as the first signing under the club's new ownership
The Italy international leaves the Rome outfit after four seasons, having made almost 200 appearances, becoming Inter's first acquisition since Suning Holdings Group took over the club.
Candreva has also played 40 times for his national team, appearing at the 2014 World Cup and Euro 2016.
"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."
Inter president Erick Thohir also expressed his delight at adding the 29-year-old to a strong squad.
"I am very pleased to welcome Antonio to Inter," he said. "I am sure that he will make a major contribution to what is already a very competitive team."