The online drama, loosely connected to its parent series, will star Sarah Roemer (The Event) and Ryan Eggold (90210).
36-year-old McPartlin has now been cast in a major role, according to TVLine.
The actor's recent credits include a recurring role on CSI: Miami and a guest spot on TV Land's Hot in Cleveland.
Touch creator Tim Kring recently revealed the premise of Daybreak, explaining: "On Touch, we recently introduced a 12-sided shape called a dodecahedron. It's a real thing, which many believe has mystical powers.
"You'll see it again in the May 31 season finale. And its journey will continue that same day in the premiere chapter of Daybreak, a series of webisodes."
Touch airs on Thursdays at 9pm on Fox in the US and on Tuesdays at 8pm on Sky1 in the UK. A second season has already been ordered. Daybreak will launch following the show's two-part season finale.
> Touch recap: Kiefer Sutherland pulls off a heist in 'Tesselations'
Watch Kiefer Sutherland discuss Touch with Digital Spy below: