On 28 July 2013, he scored his first goal in the 2013–2014 season against Szombathelyi Haladás at the Sóstói Stadion, Székesfehérvár.

[8] In July 2015, Kleinheisler refused to sign the extension of his contract with Videoton, therefore he was ousted to the reserves for the 2015–2016 season.

He was brought onto the pitch in the 62nd minute at 2–0 to Berlin and helped Bremen come back from 2–0 and 3–1 deficits to earn a 3–3 draw.

[24] On 6 November 2015, Bernd Storck announced the Hungarian national team squad for the UEFA Euro 2016 qualifying play-off match against Norway.

The biggest surprise was the inclusion of Kleinheisler because he had not played a single match in the 2015–16 Nemzeti Bajnokság I season.

[29] On 1 June 2021, Kleinheisler was included in the final 26-man squad to represent Hungary at the rescheduled UEFA Euro 2020 tournament.