The objective of the current study was to evaluate the reliability and validity of the Japanese version of the Mini-Balance Evaluation Systems Test (J-Mini-BESTest) in patients with subacute stroke. Methods: Eighteen patients who had suffered a first hemiplegic stroke (mean age, 59.1 ± 27.0 years) and had been admitted to convalescent rehabilitation wards were enrolled. The J-Mini-BESTest, the Berg Balance Scale (BBS), and the functional reach test (FRT) were used to assess balance. Four physical therapists (PTs) observed and scored the J-Mini-BESTest while another PT conducted the test. The interrater reliability of the J-Mini-BESTest was assessed using intraclass correlation coefficients (ICC[2,1]) for the total and section scores, and kappa statistics for each item. Internal consistency of the five raters was assessed using Cronbach's alpha. Concurrent validity of the J-Mini-BESTest was assessed against the BBS and FRT using Spearman's correlation coefficients. Results: The ICC[2,1] of the total and section scores were 0.90 (95% confidence interval: 0.81-0.95) and 0.63-0.85, respectively. Cronbach's alphas were 0.80-0.87. The kappa statistics were 0.47-1.00. The scores of the J-Mini-BESTest were significantly correlated with those of the BBS (rho=0.66, p=0.006) but not with those of the FRT (rho=-0.36, p= 0.189). Conclusion: The J-Mini-BESTest showed excellent inter-rater reliability and internal consistency. Although the J-Mini-BESTest was not correlated with the FRT, it was significantly correlated with the BBS. The J-Mini-BESTest is a reliable and valid tool for evaluating dynamic balance in patients with subacute stroke.