The club, which currently plays in the Scottish Championship, will become the first side in the country to adopt the world-famous pride symbol on its jersey when the 2019/20 season kicks off in mid-July.
Sporting the new LGBT-friendly away kit on Tuesday was Thistle's Joe Cardle, with fellow Firhill stars Thomas O'Ware and Jamie Sneddon on hand to launch the home and goalkeeper's kits respectively.
Commenting on the decision, Partick chief executive Gerry Britton said the club wanted to make it clear that the Glasgow side do "not accept discrimination in any form".
He said: "We were very clear when putting together the design.
"We wanted to make a statement about inclusivity and that's what inspired the rainbow feature on the away shirt.
"Partick Thistle is one club open to all, we will not accept discrimination in any form and I sincerely hope that this shows that. Football can be such a wonderful universal language that can help bridge all sorts of divides, both large and small.
"As a club, if we can use this sport that we all love to make all of our supporters feel welcome, even if that is through something as simple as a band of colour on a shirt, then it's a simple decision."
In November it was announced that Partick Thistle was backing the Rainbow Laces campaign in a bid to change attitudes in sport and make sure that LGBT people are welcomed and accepted at football matches.
All four divisions of the SPFL will kick off on the weekend of Saturday August 3.