Objective: This study aimed to compare young female kendo athletes and sex-matched non-athlete controls to determine if there are differences in handgrip strength between the groups, and if so, at what age these differences appear. Methods: Thirty-three female kendo athletes (mean age [SD]: 9.5 [1.8] years) and 33 sex-matched female non-athlete controls (mean age [SD]: 9.3 [1.8] years) between the ages of 6 and 12 years participated in this study. Handgrip strength was measured using a Smedley dynamometer, and the average value of both hands was used for analysis. The kendo experience was determined when they started practice. Handgrip strength was compared between groups. Statistical moderation was used to determine if the relationship between group and handgrip strength depended upon the age of the participant. Results: Female kendo athletes exhibited significantly higher handgrip strength compared to female non-athlete controls both before (4.5 kg [95% CI: 1.9, 7.03]) and after (2.4 kg [95% CI: 0.7, 3.9]) adjusting for body mass. Adjusting for body mass, we observed that the relationship between group and handgrip strength depended on the child's age (group Å~ age, t = 2.75, p = 0.007). Using the Johnson-Neyman procedure, we identified statistically significant differences between groups starting from 8.3 years old and above. Without adjusting for body mass, significant differences appeared from 8.0 years old and above. Below that age, differences between groups were minimal and not statistically different. Conclusion: Our findings suggest that sports (e.g., kendo) requiring grasping equipment with the hands may help improve handgrip strength in adulthood.