Obinna joins West Ham on loan
The 23-year-old passed a medical after holding talks at Upton Park and the club's training ground, West Ham said on their website.
Obinna, who began his Inter career in 2008, spent last season on loan at Spanish side Malaga. He has won 34 caps for Nigeria, and appeared twice in the World Cup in South Africa as his country were eliminated in the first round.
Obinna is West Ham's sixth acquisition for the new season. They face Manchester United at Old Trafford in the Premier League on Saturday.