Serie A - Viviano suffers bad knee injury
Viviano, who recently joined the club from Bologna, tore a ligament in his left knee.
"Tests revealed a complete tear of the anterior cruciate ligament. Surgery is required and will be planned over the next few days," Inter said in a statement.
Italian media said the player would be out for six months.
Viviano, 25, made his Italy debut last year and has six caps in total. He is the second choice keeper behind Gianluigi Buffon.