Objective This study aims to evaluate the Achilles tendon's properties after rehabilitation training in patients with stroke using real‐time ultrasound elastography. Methods A total of 24 patients with mild hemiplegic stroke in the past 6 to 12 months and unilateral lower limb movement disorder were prospectively enrolled. All patients accepted 9‐week rehabilitation training with the same schema. The 2‐dimensional elastography and real‐time elastography findings in the impaired and contralateral normal Achilles tendon were measured at pretraining and at 3, 6, and 9 weeks after training, which included tendon length, thickness, elasticity score (grade 1–3), and strain ratio of fat to tendon. The functional properties, which include the 10‐meter walk test and timed up‐and‐go scores, were evaluated before and after the 9‐week training. Results The impaired Achilles tendon had a longer length (P = .002), lower frequency of grade 1 (P = .012), and lower strain ratio (P = .009) than the contralateral tendon before training. The impaired tendons at the third, sixth, and ninth weeks after training were compared to ones before training, respectively, which revealed shorter length, increased frequency of grade 1, and increased strain ratio. The first statistically significant changes in the length were observed at the sixth week, while such changes in elasticity score and strain ratio were observed at the ninth week. Conclusions Two‐dimensional elastography and real‐time elastography can provide valuable imaging markers for quantitatively evaluating the Achilles tendon's properties after rehabilitation training in patients with stroke.