Allan Moore yesterday confirmed the player has signed a pre-contract agreement to join when his Blues deal expires next month.
The Ton boss had originally refused to be drawn on suggestions he had agreed terms with the 22-year-old while the Stair Park club were still to compete in the end of season play-offs.
But after Stranraer lost on penalties to Albion Rovers on Sunday, Moore was delighted to announce that Stirling would be a Ton player next season.
Moore told the Tele: "The contract with Stephen Stirling is agreed and he will join us when his deal with Stranraer expires next month.
"We have had it agreed for a while but I didn't want to say anything until after the play-offs because Stranraer were playing in them and I thought it would be disrespectful to the player and his club. We had Stephen on trial last summer and he was very impressive, but by that stage I had already used up my budget so we couldn't offer him anything.
"I kept my eye on him over the season and stayed in touch with Stevie Aitken and Chris Aitken, who I'm good friends with down at Stranraer and they both rate him very highly.
"Former Morton defender David MacGregor was speaking to me about him recently and he said he thought he was a quality player.
"I went down for the first leg of their play-off final against Albion Rovers and he played well in that one too, so I'm delighted to have been able to sign him for next season."
The former Scotland Under-19 central midfielder has been a standout at Third Division level and was included in PFA Scotland's Third Division team of the year.And Moore is convinced Stirling has what it takes to step up two divisions and transfer that form to Scottish football's second tier.
He added: "We'll find out if he can make the jump up to the First Division, but I'm confident he can.
"He was highly rated at Rangers and then went on loan to Stirling, where he scored a double against us on the last day of last season.
"Rangers released him and then he came to us on trial, but what really impressed me was the way he went to Stranraer with a great attitude and desire to kick-start his career. He scored 12 goals last season. He's always looking to make a forward pass and then follow the pass to get beyond the strikers - and that was something we didn't have last season.
"The boy takes a good free-kick and scored a few last season. At the end of the day, the goals are the same size no matter what division you're playing in.
"He's another young boy who's at the right age to kick on, and we're hoping he'll work well with Michael Tidser in the middle."