On 4 August 2009, it was said that Arnautović was on the verge of a move to Italian giants Inter Milan. The deal had been largely held up due to a stress fracture in Arnautović's right foot, leading to a re-negotiation of the deal between the clubs. On 6 August, it was announced by Twente that the details for the loan had been finalised, Arnautović would join Inter on loan for the season. The deal was said to become permanent if he was to play a set number of matches. If the deal did not become permanent the player would return to Twente on a pre-agreed contract of two years, with an option to extend the contract for a third year. He made his unofficial debut for Inter in a friendly match on 5 September 2009 against Swiss team, Lugano, the final score was 3–3.