The 36-year-old called time on his playing days at the end of the season, having spent the last eight games exclusively on the touchline as a first-team coach.
He had previously spent time as a stand-in coach when Frankie McAvoy was ill with Covid earlier on in the season, and remained an influence on the touchline prior to Alex Neil’s departure.
Gallagher’s retirement ended eight consecutive seasons as a PNE player, with a further season on loan earlier in his career.
The former club captain played 313 times for the Lilywhites, scoring 44 times, and sits 23rd in the all-time appearance list at Deepdale.
He returned to the club on loan in 2013, six years after his first temporary spell.
In his first season back North End were defeated by Rotherham United in the League One play-off semi-final but that only strengthened his resolve to stay at the club.
Gallagher told the Lancashire Post: “There have been so many moments that I’ve enjoyed.
“My first goal that I scored, against Sheffield Wednesday in 2007, when I was still a young boy learning my trade.
“Coming back and the pain of Rotherham away in the play-off semi-final. That made me so determined to come back the next year.
“I wanted it boxed off and done knowing that we had a great footballing team that Simon Grayson had put together – Joe Garner, Jermaine Beckford and Tom Clarke to name a few.
“We had a really strong team and I believed we could achieve something special.”
There will only be one winner when it comes to Gallagher’s favourite moment in a PNE shirt – the 2015 play-off final.
The former No.12 set up two goals as PNE won 4-0 against Swindon Town on Wembley six years ago.
He said: “But what I will say, as a player, if you ever get the chance to go to Wembley and win, it’s an incredible feeling.
“It’s not easy but when we went into those play-offs we absolutely took teams to pieces. We didn’t concede a goal. To win at Wembley and see the faces on the supporters, because I know the heartache they’ve had over the years in the play-offs.
“Just to put that curse to bed and celebrate the win with the supporters is something that will live with me forever.
“To have my family there to watch me play at Wembley, and win at Wembley, was just incredible.
“There have been so many memories. It’s been an incredible journey and something I’m really proud of.”