He started to play handball at the age of 10 in Lemgo, where his father, Lajos Mocsai was in charge at that time.

[2] He switched to domestic rivals and Champions League aspirants Pfadi Winterthur in 2004 to replace Cho Chi-Hyo, who was transferred to Wacker Thun.

[3] Mocsai signed a two-year deal with his new team, however, the bad performances and the restructure of the board resulted a mass exodus in 2005.

With the North Rhine-Westphalian team he won the EHF Cup in 2010, after beating Kadetten Schaffhausen in the finals.

Between 2010 and 2012 he played for SG Flensburg-Handewitt, subsequently he signed a two-year contract with Bundesliga rivals TSV Hannover-Burgdorf.