The defender has been one of the key players for the Mother City club after being signed by former coach Benni McCarthy.
Seedat joins TS Galaxy after the club bought the top flight status of Highlands Park. The former Nedbank Cup champions will be campaigning in the newly DSTV sponsored top tier.
The Citizens are set to lose another key player in Kermit Erasmus who is expected to join Mamelodi Sundowns in the off-season transfer window.
Erasmus is set to join Sundowns before the start of the 2020/2021.
“City bids farewell to a true servant of the club Ebrahim Seedat. Ebi joins TS Galaxy, having been a stalwart since 2016. Always part of the family, good luck in the next phase of your career Ebi!,” read a statement from City.