The club have announced that due to the number of Covid cases and injuries among the Jags squad, they are unable to fulfil the Championship fixture.
A rescheduled date for the fixture has yet to be confirmed.
A Thistle spokesperson said: “Our cinch Championship fixture against Greenock Morton has been postponed following positive covid tests within the Thistle squad.
“The number of positive tests, in addition to the current number of injuries within the team, left the club unable to fulfil tomorrow’s match with Greenock Morton.
“The individuals will not be named due to medical confidentiality and those affected with now self-isolate in line with current protocols.
“A re-scheduled date for this fixture will be announced in due course.
“All supporters who have purchased a PPV pass for this fixture will receive an automatic refund.”
The SPFL also commented on the matter, while revealing that Clyde vs Queen’s Park had also been called off tomorrow after a request from the managerless Spiders.
It reads: “The SPFL can confirm that following requests from Partick Thistle and Queen’s Park, their games tomorrow have been postponed.
“The clubs do not have sufficient players available to fulfil the fixtures because of Covid cases. New dates for the matches will be confirmed in due course.”