The broadcaster originally ordered 10 episodes of the semi-improvised crime drama and has aired five.
The five remaining instalments, plus some new episodes, will now form series two in the autumn, with an all-new third series also confirmed for 2015.
Ben Frow, Channel 5's Director of Programmes, said: "Suspects has been an incredible critical success for Channel 5, and praised for its innovative and game-changing approach to procedural drama.
"We're thrilled by the reaction and are excited about commissioning a further series for later in the year."
Fay Ripley, Damien Molony and Claire-Hope Ashitey star in Suspects. Working without a traditional script, the cast improvise their dialogue and actions based on a detailed plot synopsis.
Devised by Paul Marquess (The Bill, Footballers' Wives), the series is Channel 5's first original drama for eight years.
Suspects - Channel 5's stripped back cop drama: "It's electrifying"
Watch a clip from Channel 5's Suspects below: