This study aimed to determine whether the degree of pes planus was associated with hallux valgus severity and hallux valgus surgery outcomes. A total of 122 feet were retrospectively analyzed after hallux valgus surgery. The hallux valgus angle, inter-metatarsal angle, lateral talo-first metatarsal angle, calcaneal pitch, and talonavicular coverage angle were measured. The Foot and Ankle Outcome Score and Foot Function Index were evaluated. A significant correlation between radiographic parameters of pes planus and hallux valgus severity, radiographic outcomes, Foot and Ankle Outcome Score, and Foot Function Index were not noted. The hallux valgus angle and inter-metatarsal angle changed significantly after the surgery (p < .001 and p < .001, respectively); however, a significant difference was not noted between the pes planus and non-pes planus groups (p = .279 and p = .632, respectively). A significant interaction between the time points and groups was not observed with respect to the hallux valgus angle (p = .311) and inter-metatarsal angle (p = .417). Multivariable logistic regression revealed that none of the radiographic parameters for pes planus affected hallux valgus recurrence. Pes planus in adult patients is not significantly associated with hallux valgus severity and recurrence, radiographic outcomes, or clinical scores.