•Different factor structures of the SFT were observed among women and men older adults.•The factor structure of the SFT was better represented by a second-order 4-factor model for men sample.•The factor structure of the SFT was better represented by a second-order 5-factor model for women sample.•BMI was not significantly associated with the latent variable of functional fitness in the men sample.•Normal body weight and overweight participants responded to the SFT testing items in similar ways. This study examined the factor structure of the Senior Fitness Test and examined its measurement and structural invariance across participants with normal body weight and participants who were overweight. Eight hundred and forty-five community-dwelling older adults in Hong Kong participated in this study. Their functional fitness was assessed using the Senior Fitness Test. Confirmatory factor analysis was conducted to examine and compare two competing models: a one-factor model and a second-order model. Multiple-group confirmatory factor analysis was conducted to evaluate the measurement and structural invariance of the SFT measurement model. Multiple fit indices were used to evaluate the adequacy of the model fit to the data. The second-order model outperformed the one-factor model. For men participants, the second-order 4-factor model was indicated, while for women participants, the second-order 5-factor model was evidenced. The measurement and structural invariance of the SFT measurement model across normal weight and overweight participants were also supported. This study provided initial evidence for the construct validity of the SFT. However, there were some differences in the factor structure of the SFT for men and women participants. Body composition did not necessarily reflect the functional fitness of men participants. All of the older adults responded to the testing items in a similar way regardless of body weight status in both men and women samples. The significance of each component for functional fitness was also similar for participants with different body weight statuses.