Carlin will join Formula 3 European Championship rival Prema in expanding its line-up for 2018, having signed Nikita Troitskiy as its fifth driver.
F3 teams ran no more than four full-season entries last year due to championship regulations, but the FIA relaxing its restrictions has paved way for two of the series' leading outfits to increase their presence.
After Prema recently named Mick Schumacher as its fifth signing for 2018, Carlin - which ran as many as six full-season entries in '15 - has now added Euroformula Open runner-up Troitskiy to its previously confirmed quartet of Jehan Daruvala, Ferdinand Habsburg, Devlin DeFrancesco and Sacha Fenestraz.
"It's nice to be a part of such a strong team as Carlin for the 2018 season," Troitskiy said.
"The team all work together and do their job perfectly well so I look forward to joining them. I will do my best to show the highest result in 2018."
Carlin was beaten by Prema in the teams' standings last year, but ended Prema's six-year stronghold on drivers' honours by taking McLaren junior Lando Norris to the title.
Finnish-born Russian driver Troitskiy is the second SMP-backed rookie to sign up for European F3 in 2018, alongside Ferrari junior Robert Shwartzman at Prema.
Now entering his fourth season in car racing, 18-year-old Troitskiy was a race-winner in the SMP-run Northern European F4 series and the off-season MRF Challenge, before finishing runner-up to a dominant Harrison Scott in Euroformula last year.
"Nikita is a driver who we have competed against in the past and watched with interest in championships he has raced in," said team boss Trevor Carlin.
"He is a very dedicated and determined driver and will be a fantastic addition to our FIA Formula 3 European team.
"We have another great line-up ahead of the 2018 season."
Euro F3 line-up so far
Carlin: Jehan Daruvala, Devlin DeFrancesco, Sacha Fenestraz, Ferdinand Habsburg, Nikita Troitskiy
Motopark: Dan Ticktum, Marino Sato, Fabio Scherer, Jonathan Aberdein
Prema Powerteam: Marcus Armstrong, Robert Shwartzman, Ralf Aron, Guan Yu Zhou, Mick Schumacher
Hitech GP: Enaam Ahmed, Alex Palou, Ben Hingeley
Van Amersfoort Racing: Keyvan Andres
Fortec Motorsport: TBA