 Bundesliga club SV Sandhausen, where he signed a one-and-a-half year contract.He made 16 league appearances during the second half of the 2018–19 season in which the club avoided relegation.Prior to the 2019–20 season, Diekmeier signed a contract extension keeping him in Sandhausen until 2022, and was also appointed vice-captain by head coach Uwe Koschinat.