Both players have signed two-year contracts, meaning they'll be staying at Scotstoun until at least May 2017.
Winger Seymour joined the GUINNESS PRO12 side in 2011 and has gone on to make 62 appearances, scoring 20 tries.
The 26-year-old has 13 caps for Scotland and has scored six tries for his country, including a touchdown in each of the three November viagogo Autumn Tests against Argentina, New Zealand and Tonga.
Tommy Seymour said: "I'm really enjoying my rugby and I'm very happy to be staying at the Warriors.
"The four years I've been at the club have been hugely enjoyable and we've come on really strongly as a team and our identity has grown.
"My coaches and teammates have helped me massively in my development as a player and I'm delighted I get to spend another two years continuing that development, playing in front of a crowd that is second to none."
Pyrgos, who has been at the Warriors since 2010, has made 90 appearances for the club and has scored 54 points.
The 25-year-old scrum-half has 13 caps for his country, with two tries to his name.
Henry Pyrgos said: "It's been great to see the club grow since I've been here and I'm looking forward to playing in front of our really passionate supporters for another two years. Scotstoun has become a real home for us.
"Captaining the team has been a huge honour and I'm delighted to be staying in Glasgow. I believe we've got a squad capable of winning trophies.
"Playing for the Warriors has enabled me to play for my country and I believe being at Glasgow gives me the opportunity to push on for more caps."
Glasgow Warriors head coach Gregor Townsend added: "This is another boost for the club as we continue to shape our squad for next season.
"Tommy and Henry have worked hard to improve their games and have been in great form this season.
"They have been at the club for a few years now and are in a position to be key drivers of our development on and off the field."
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland