The purpose of this study was to compare the effects of different injection technique guidance with electrical stimulation (ES) vs ultrasonography (USG) of botulinum toxin A injection (BoNT A) in post-stroke patients with plantar flexor spasticity. Forty chronic post-stroke patients with plantar flexor spasticity and who were able to walk were included in the study. They were randomized into two groups: in 20 patients the BoNT A injection was applied with the guidance of ES and in 20 patients with the guidance of USG by the same physician. Gastrocnemius, soleus, and tibialis posterior were injected. Spasticity was evaluated by ashworth scale; the functional status was evaluated by ankle goniometry for range of motion, Brunnstrom stages, Barthel Index, and 10-m walk test before the treatment, 2nd week, and 3rd month after the treatment. Statistical significance was defined as p < 0.05. Two groups were similar in respect to demographical and clinical features. In both groups, walking speed and range of motion increased significantly after the treatment. When the two groups were compared at 3rd month after the treatment; range of motion of the ankle joint plantar flexion and dorsiflexion when knee in extension showed a significant difference between the two groups. Ashworth scale, Brunnstrom stages, Barthel index, walking speed tests, and other ankle goniometry for range of motion showed no statistically significant difference between two groups. We can conclude that USG and ES guidence are both effective injection techniques when applying BoNT A to ankle plantar flexor muscles.