Barclay named Scotland captain for June tour
Barclay, 30, takes over from regular captain Greig Laidlaw, who has received a late call-up to the British and Irish Lions squad.
Townsend has also selected three uncapped players in Glasgow centre Nick Grigg, Glasgow prop D'Arcy Rae and Edinburgh hooker George Turner.
"We're looking forward to what will be a challenging tour of three different countries, playing three quality sides," Townsend said in a press release.
"This tour is all about learning and competing. As a coaching group, we will be learning more about our players and how they perform in a different environment against three sides with contrasting styles of play.
"We have assembled a strong squad and this is an opportunity for them to work with us for the first time."
Townsend has selected his first squad since succeeding Vern Cotter as head coach.
Barclay captained Scotland for the final three matches of this year's Six Nations after Laidlaw had to withdraw from the squad due to an ankle injury.
Peter Horne and Willem Nel return from injury, while there are recalls for Glasgow wing Lee Jones, Harlequins back Ruaridh Jackson and Edinburgh scrumhalf Sam Hidalgo-Clyne.
Grant Gilchrist, Cornel Du Preez, Duncan Weir, Simon Berghan and Stuart McInally were all overlooked.
Scotland play Italy in Singapore on June 10, followed by Australia in Sydney on June 17 and Fiji in Suva on June 24.
"Playing Italy in Singapore will be a very different prospect than taking them on in Edinburgh or Rome. It will be a challenge for both teams to adapt to the new surroundings," Townsend added.
"Australia in Sydney in the afternoon is just an excellent fixture against a team that plays some great attacking rugby, while Fiji in Suva will be a huge test for our defence in an environment that we will very rarely play in."
Scotland squad:
Forwards: Alex Allan (Glasgow), Allan Dell (Edinburgh), Zander Fagerson (Glasgow), Willem Nel (Edinburgh), D'Arcy Rae (Glasgow), Gordon Reid (Glasgow), Fraser Brown (Glasgow), Ross Ford (Edinburgh), George Turner (Edinburgh), Richie Gray (Toulouse/FRA), Jonny Gray (Glasgow), Tim Swinson (Glasgow), Ben Toolis (Edinburgh), John Barclay (captain, Scarlets/WAL), Magnus Bradbury (Edinburgh), John Hardie (Edinburgh), Rob Harley (Glasgow), Josh Strauss (Glasgow), Hamish Watson (Edinburgh), Ryan Wilson (Glasgow)
Backs: Sam Hidalgo-Clyne (Edinburgh), Ali Price (Glasgow), Henry Pyrgos (Glasgow), Peter Horne (Glasgow), Finn Russell (Glasgow), Alex Dunbar (Glasgow), Nick Grigg (Glasgow), Matt Scott (Gloucester/ENG), Duncan Taylor (Saracens/ENG), Damien Hoyland (Edinburgh), Ruaridh Jackson (Harlequins/ENG), Lee Jones (Glasgow), Sean Maitland (Saracens/ENG), Tim Visser (Harlequins/ENG)
Agence France-Presse