PAT1 homolog 2 (PATL2), encoding an RNA-binding protein, is a repressor involved in the translational regulation of maternal mRNAs during oocyte maturation. Previous studies have reported mutations inPATL2those led to female infertility with oocyte maturation arrest; however, the mechanisms by which mutations affected meiotic maturation remained unclear. Here, we identified several novel and recurrent mutations ofPATL2in patients with similar phenotype, and chose the missense mutation c.649 T>A p.Tyr217Asn inPATL2(PATL2^Y217N) as a typical to investigate the underlying mechanisms. We confirmed that this mutation disturbed oocyte maturation and observed morphological defects of large polar body, symmetrical division and abnormal spindle after microinjection of corresponding mutated mRNA. We further evaluated the effect of the PATL2^Y217Nmutation in 293T cells, and found this mutation decreased the ubiquitination level and degradation of PATL2. Then, abnormally increased PATL2 bound mRNAs of Mos, an upstream activator of mitogen activated protein kinase (MAPK), to regulate its translational activity and subsequently impaired MAPK signaling pathway and oocyte meiosis. These results dissented from the previous view thatPATL2mutations reduced their expression and highlight the role of PATL2 in translational regulation of Mos and its association with MAPK signaling pathway during oocyte meiotic maturation.