Introduction It is a common practice among strength and conditioning coaches to conduct proprioception training before a regular training session when athletes are in a rested state, but it is known that the majority of injuries occurred at the end of the training session, or competition, when athletes are fatigued (Hawkins and Fuller, 1999). Therefore, the aim of this study was to investigate the effects of basketball training on single-leg balance ability in rested and fatigued state and assess whether the efficiency of a proprioception program is affected by its performance before or after a regular basketball training. Methods Thirty-three female basketball players were randomly divided into three subgroups (n=11 each). Experimental groups E1 and E2 performed the same proprioception program (8 weeks, 3 times per week, 15-20 minutes per session), but E1 performed before, and E2 after regular basketball training session. A control group performed only the regular basketball training. The Biodex Balance System was used to assess single-leg balance ability, overall stability index (OSI) prior to the utilization of the program (in a rested and fatigued state), as well as after the program. General fatigue was induced by the beep test protocol. Two separate 3-way repeated measures ANOVA (time x group x condition) and multiple pairwise comparisons were used to test the differences in the single-leg balance ability between and within the groups pre- and post-proprioception program,and to determine if the timing of the proprioception training (pre-training vs. post-training) affected the balance ability in rested and fatigued state. Results The enhancement in single-leg balance ability for both dominant and non-dominant leg was higher in the experimental groups than in the control group (> 15%). Greater improvement was in a dominant leg’s OSI in the fatigued and non-fatigued state in E2 group. E1 group showed similar improvement in the rested state for non-dominant leg compared to E2 group. Discussion We found that a basketball training improved single-leg ability, but greater enhancement was observed when the proprioception training was added. Additionally, we found that the post-training proprioception program positively affected balance ability in the rested and fatigued state. These findings are in accordance with Gioftsidou et al. (2006). It seems that training in the fatigued state (post-training) has a positive transfer on single-leg ability in the fatigued state, so it is recommended to conduct it after a training session or after exhausting exercises.