St Mirren made it a hat-trick of signings on Monday by adding Scott Tanser to the earlier captures of Greg Kiltie and Curtis Main.
Left-back Tanser, 26, has signed a one-year contract with the option of a further year after opting to leave St Johnstone.
Kiltie, 24, decided to leave Kilmarnock last week after a 12-year association with the Ayrshire side following their relegation to the Championship.
Former Motherwell and Aberdeen striker Main left Pittodrie back in January after signing for Shrewsbury on a short-term deal.
But he is now back in Scotland after joining Kiltie in agreeing a two-year deal with the Buddies.
Manager Jim Goodwin – who had already added Motherwell defender Charles Dunne to his squad for next season – said: "Greg is a really good young player. He has had a really good season in a Kilmarnock team that has struggled, to be perfectly honest.
"He's very creative, very direct, and positive in his thinking when he receives the ball, he wants to go forward, he wants to get shots off and tries to create good goal-scoring opportunities for his team-mates around him.
"It's another good character and we have great references on him, he is a pleasure to work with by all accounts, so I am really looking forward to getting him and to work closely with him as soon as pre-season starts next week.
"Not only will he assist goals but hopefully he'll chip in with his fair share as well. We certainly saw that at close quarters in recent games where I thought he was excellent against us.
"Curtis is a physical, strong centre-forward who will be a great addition to the squad and gives me four very good strikers now to choose from with Eamonn Brophy, Kristian Dennis and Lee Erwin as well.
"I'm really pleased to get Curtis in. He's the right character for us as well, he's the right temperament and a real leader both on and off the pitch.
"I'm just delighted we are able to get it over the line. to be honest."
Kiltie began his Killie career against St Mirren as a 16-year-old. The midfield playmaker would go on to make over 100 appearances for Kilmarnock as well as having loan spells at Queen of the South, Morton and Dunfermline.
He said: "I spoke to the manager and he explained about the club and it's the right fit.
"The club sells itself. It's a very good club and showing ambition in terms of where it wants to get to as well.
"I play in front of the midfield and try to create opportunities or chip in with some goals so that's hopefully what I can do.
"I can't wait to get back at it with a new challenge ahead. I'm delighted to be here and can't wait to get going."
Main added: "I'm really excited to be here.
"I've spoken to the manager on numerous occasions over the last couple of months and I'm finally here and looking forward to the challenge.
"The manager wanted to bring me to the club to do what he knows I'm capable of doing. Having that backing and belief from the manager is a key thing for anyone coming into the club.
"I'll always give everything. I'm quick, strong and powerful and I love to win."
