He made his league debut in a 1–0 away victory against Chievo on 6 January 2010. He played in their next match against Siena coming on as a substitute at half time for the injured Dejan Stanković and helped Inter to win the match 4–3. He played one more match for Inter against Atalanta on 24 April 2010. At the end of the season Inter decided against turning his loan in a permanent move and José Mourinho stated that Arnautović "is a fantastic person but has the attitude of a child".