Objectives Resistance training (RT) is emerging as a training modality to improve motor function and facilitate physical activity participation in children across the motor proficiency spectrum. Although RT competency assessments have been established and validated among adolescent cohorts, the extent to which these methods are suitable for assessing children’s RT skills is unknown. This project aimed to assess the psychometric properties of the adapted Resistance Training Skills Battery for Children (RTSBc), in children with varying motor proficiency. Design Repeated measures design with 40 participants (M age=8.2±1.7years) displaying varying levels of motor proficiency. Methods Participants performed the adapted RTSBc on two occasions, receiving a score for their execution of each component, in addition to an overall RT skill quotient child (RTSQc). Cronbach’s alpha, intra-class correlation (ICC), Bland–Altman analysis, and typical error were used to assess test–retest reliability. To examine construct validity, exploratory factor analysis was performed alongside computing correlations between participants’ muscle strength, motor proficiency, age, lean muscle mass, and RTSQc. Results The RTSBc displayed an acceptable level of internal consistency (alpha=0.86) and test–retest reliability (ICC range=0.86–0.99). Exploratory factor analysis supported internal test structure, with all six RT skills loading strongly on a single factor (range 0.56–0.89). Analyses of structural validity revealed positive correlations for RTSQc in relation to motor proficiency (r=0.52, p<0.001) and strength scores (r=0.61, p<0.001). Conclusions Analyses revealed support for the construct validity and test–retest reliability of the RTSBc, providing preliminary evidence that the RTSBc is appropriate for use in the assessment of children’s RT competency.