Posterior crossbite may affect craniofacial growth and development. Thus, this study aimed to associate facial dimensions (by standardized frontal photographs) to masseter and anterior portion of the temporal muscle thickness (by ultrasonography) and maximal bilateral bite force in 49 children with deciduous and early mixed dentitions. They were distributed in four groups: deciduous-normal occlusion (DNO, n = 15), deciduous-crossbite (DCB, n = 10), mixed-normal occlusion (MNO, n = 13) and mixed-crossbite (MCB, n = 11). Anterior facial height (AFH), bizygomatic width (FWB), and intergonial width (FWI) were determined and associated with muscle thickness and bite force, applying Pearsons coefficients and multiple logistic regression, with age, gender, body weight and height as the covariates. FWB and FWI were correlated positively with the masseter thickness, whereas AFH/FWB and AFH/FWI ratios had negative correlation, except in the DNO group. The correlation between AFH/FWB and bite force in the MCB group was significantly negative. A higher AFH/FWB in MNO and MCB led to a significantly higher probability for functional crossbite development. In the studied sample, it was observed that children in the early mixed dentition with a long-face trend showed lower bite force and higher probability to present functional posterior crossbite, without significant influence of the covariates.