Although time since amputation (TSAmp) is recognized as a primary factor influencing the walking ability of individuals with unilateral transfemoral amputation (uTFA), the specific effects of TSAmp on gait asymmetry remain insufficiently investigated. This study aimed to clarify whether gait asymmetry decrease with longer TSAmp across a range of walking speeds. Thirty individuals with uTFA, classified as K-3 and K-4 functional levels, participated in this study. Participants walked at eight speeds (ranging from 2.0 to 5.5 km/h in increments of 0.5 km/h) on an instrumented treadmill. Spatiotemporal parameters and peak values of ground reaction forces (GRFs), including anteroposterior, mediolateral, and vertical components, were measured to calculate the asymmetry ratio. Linear regression analyses were subsequently conducted to examine the relationships between TSAmp, TSAmp/Age (age-normalized TSAmp), and the asymmetry ratio. The results demonstrated no significant correlations between TSAmp, TSAmp/Age, and the asymmetry ratio across all measured parameters and walking speeds. These findings suggest that TSAmp and TSAmp/Age exhibit weak associations with gait asymmetry in terms of spatiotemporal parameters and peak GRFs. The results of the present study suggest that neither TSAmp nor TSAmp/Age are necessarily associated with gait asymmetry. Therefore, predicting gait asymmetry in individuals with uTFA based solely on TSAmp is not feasible.