Exome sequencing of ovarian clear-cell carcinoma has identified somatic mutations in PPP2R1A, a subunit of protein phosphatase 2A. The present study was performed to determine the frequency of PPP2R1A mutations in exon 5, which harbors previously reported mutation hot spots, and adjacent exon 6, in 209 ovarian and 56 uterine tumors of various histologic subtypes. PPP2R1A mutations were demonstrated in 10 of 110 type I ovarian tumors (9.1%) including low-grade serous, low-grade endometrioid, clear-cell, and mucinous carcinomas. In contrast, none of 71 type II ovarian (high-grade serous) carcinomas exhibited PPP2R1A mutations. Moreover, PPP2R1A mutations were observed in 2 of 30 type I uterine (endometrioid) carcinomas (6.7%) and 5 of 26 type II uterine (serous) carcinomas (19.2%). Of the 18 mutations, 13 affected the R182 or 183, and there were 5 novel mutations including 3 involving S256, 1 involving W257, and 1 involving P179. All mutations were located in the α-helix repeats near the interface between the A subunit and the regulatory B subunit of the enzyme complex. These data provide new evidence that PPP2R1A somatic mutations occur in certain types of uterine and ovarian neoplastic lesions, especially uterine serous carcinomas, and suggest that mutation of PPP2R1A may participate in the pathogenesis of ovarian type I and uterine type II carcinomas.