This study examined the relationship between body mass index (BMI), Sex, and Fundamental Movement Skills (FMS) performance among low-income rural children aged 5 to 7 years. 39 children (20 boys and 19 girls) participated in the study. FMS proficiency was evaluated using the Furtado-Gallagher Child Observational Movement Pattern Assessment System (FG-COMPASS). The children’s height and weight were measured to calculate BMI, which was then classified into ‘normal weight’ and 'overweight'. A two-way factorial ANOVA assessed the effects of sex and BMI group on manipulative fundamental motor skills (MFMS), locomotor fundamental motor skills (LFMS), and total fundamental motor skills (TFMS). We hypothesized that normal weight children would outperform their overweight counterparts in locomotor (LFMS), manipulative (MFMS), and total (TFMS) fundamental motor skills and that boys would outperform girls on MFMS and TFMS but not on LFMS. Our findings showed a significant main effect of sex on MFMS, with boys performing significantly better than girls. However, no significant main effects were found for LFMS or TFMS based on sex or BMI group. Furthermore, Pearson correlation analysis revealed weak, negative, non-significant correlations between BMI percentiles and all three motor skill scores. The study’s results highlight the importance of considering sex differences when assessing FMS in children and indicate that overweight status may not necessarily relate to poorer motor skill performance in a rural, low-income context. Further research should ensure a balanced representation across BMI categories and explore the potential influence of demographic factors on motor skill development.