The symmetry of masticatory muscles activation may influence postural control and, consequently, sports performance. In basketball, where shooting accuracy is crucial, masticatory muscles symmetrical contraction remains unexplored despite its potential impact on performance. This cross-sectional study was conducted to evaluate whether symmetrical activation of the masseter and temporalis muscles impacts free-throw accuracy in non-elite female basketball players. The study included 25 players who performed 18 free-throws in each of three randomized mandibular positions: mandibular rest, maximum intercuspation, and interdental cotton rolls. Electromyographic activity of the masticatory muscles was recorded before the trials and during each free-throw. We observed that symmetrical (SYM) activation performance of the temporalis muscle in maximum voluntary contraction (MVC) negatively correlated with free-throw accuracy in the resting mandibular position (r(23) = −0.442, p = 0.027, r2 = 0.195). In maximum intercuspation, SYM activation correlated with accuracy (r(23) = 0.582, p = 0.002, r2 = 0.339). Participants with higher SYM activation values (≥ 80%) performed better (t(23) = −2.79, p = 0.010, g = −1.08). Thus, masticatory muscle symmetry relates to free-throw accuracy. Higher masseter SYM values in maximum intercuspation lead to better performance. Intraoral devices may help enhance masticatory SYM activation, potentially improving basketball free-throw performance.