PERK (EIF2AK3) is an ER-resident eIF2α kinase required for memory flexibility and metabotropic glutamate receptor-dependent long-term depression， processes known to be dependent on new protein synthesis. Here we investigated PERK's role in working memory， a cognitive ability that is independent of new protein synthesis， but instead is dependent on cellular Ca2+ dynamics. We found that working memory is impaired in forebrain-specific Perk knockout and pharmacologically PERK-inhibited mice. Moreover， inhibition of PERK in wild-type mice mimics the fear extinction impairment observed in forebrain-specific Perk knockout mice. Our findings reveal a novel role of PERK in cognitive functions and suggest that PERK regulates both Ca2+ -dependent working memory and protein synthesis-dependent memory flexibility.