The That '70s Show star will play a love interest for Sabrina's mother Tamara (Melanie Griffith), Entertainment Weekly reports.
Valderrama is expected to appear in at least three episodes of the Fox comedy, which returns to the US on October 2.
The 32-year-old actor recently starred on short-lived NBC drama Awake opposite Jason Isaacs.
His other recent TV credits include episodes of Suburgatory and Royal Pains.
Raising Hope airs on Fox in the US and on Sky1 in the UK.
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Watch a clip from Raising Hope below: