Mutations in the TP63 gene cause several syndromic disorders, including ankyloblepharon–ectodermal defects–cleft lip/palate (AEC) syndrome, characterized by severe skin erosions, cleft palate, and ectodermal dysplasia. These mutations often affect the carboxy-terminal sterile-α-motif (SAM) domain of the p63 protein, leading to domain misfolding, protein aggregation, and impaired transcriptional activity. To dissect the molecular mechanisms underlying AEC pathogenesis, we investigated primary keratinocytes derived from p63L514F mutant mice, which carry a SAM domain mutation associated with AEC syndrome. p63L514F keratinocytes exhibited significantly reduced proliferation compared to wild-type controls, as indicated by decreased 5-ethynyl-2′-deoxyuridine (EdU) incorporation, decreased Cyclin D1 and Cyclin D2 expression, and an increase in the cell-cycle inhibitors p21 and p27. Furthermore, p63L514F keratinocytes showed increased cell death, elevated reactive oxygen species (ROS) levels, and a decreased reduced (GSH) and oxidized (GSSG) glutathione (GSH/GSSG) ratio, indicating oxidative stress. This stress response was accompanied by a marked reduction in Solute Carrier Family 7 Member 11 (Slc7a11), a critical regulator of antioxidant defense. We further identified Slc7a11 as a likely direct transcriptional target of p63: p63 depletion reduced Slc7a11 expression, and chromatin immunoprecipitation uncovered an evolutionary conserved p63-binding enhancer upstream of the Slc7a11 promoter. Together, our findings demonstrate that p63 mutations causative of AEC syndrome impair keratinocyte proliferation, promote cell death via oxidative stress, and compromised antioxidant defenses, revealing a dual role for p63 in sustaining skin homeostasis.