He played for Bangladesh in two ICC Under-19 World Cups: in Australia in 2012 and in Abu Dhabi in 2013–14.

[3] At the age of 17, Mosaddek made a century in his second List A match when he scored 100 for Abahani Limited against Prime Doleshwar Sporting Club in 2013–14.

[5] After the 2013–14 season, Cricinfo named him as one of Bangladesh's most promising young players, noting that as a batsman he impressed "with his footwork against spin and ease against pace".

[14] In October 2018, Mossadek was named in the squad for the Chittagong Vikings team, following the draft for the 2018–19 Bangladesh Premier League.

[15] He captained Abahani Limited to victory in the 2018–19 Dhaka Premier Division Cricket League.

In November 2019, he was selected to play for the Sylhet Thunder in the 2019–20 Bangladesh Premier League.

[19] In February 2017, Mosaddek was added to Bangladesh's Test squad ahead of their one-off match against India after Imrul Kayes was injured.

[24][25] The International Cricket Council (ICC) named him as one of the five surprise picks for the tournament.