On 27 July 2014, Arsenal had confirmed that Ospina had signed for the club on for an undisclosed fee, believed to be £3 million, on a four-year deal. Through the club's official Instagram account, Arsenal revealed that Ospina would wear the number 13 shirt for the club, last worn by loanee Emiliano Viviano. On 23 September 2014, Ospina made his debut for Arsenal in the League Cup match against Southampton, a 2–1 home defeat. He made his second Arsenal appearance on 1 October in their UEFA Champions League group stage match at home to Galatasaray, replacing Alexis Sánchez after starting goalkeeper Wojciech Szczęsny had been sent off for a professional foul on Burak Yılmaz. Ospina conceded the penalty, taken by its earner, but Arsenal won 4–1, making several vital saves in the process. In October, Ospina suffered a thigh injury that would keep him out effectively for the rest of the 2014 calendar year. Ospina resumed his cup duties in a 2–0 win against Hull City, but maintained his place for his full Premier League debut a week later, keeping a clean sheet in a 3–0 win against Stoke City. With first-choice goalkeeper Szczęsny punished for smoking in the dressing room after a game against Southampton, Ospina was made first choice in the league and went on to claim successive clean sheets against Manchester City and Aston Villa. He played every remaining league game until the end of the season, with the exception of FA Cup ties against Brighton &amp; Hove Albion, Middlesbrough, Manchester United and Reading. Moreover, he was also an unused substitute in Arsenal's 4–0 win in the 2015 FA Cup Final against Aston Villa. However, Ospina's performances earned him a place on the FIFA Ballon d'Or longlist for the 2015 campaign.