Objective: In patients with hemiplegia, botulinum toxin type A injection for ankle spasticity of the plantar flexors reportedly improves walking speed. This improvement may be affected by background factors and patient baseline physical performance. This study aimed to clarify the factors affecting gait velocity improvement after botulinum toxin type A injection. Methods: Background and evaluation data were collected for 60 patients with stroke who received botulinum toxin type A injection for spasticity of the plantar flexors. The patients were divided into improvement (n=27) and non-improvement (n=33) groups based on the gait velocity change from before injection to 2 weeks after injection. Logistic regression analysis was performed with the improvement and non-improvement groups as response variables and background data and evaluation data at baseline as explanatory variables. Results: The presence or absence of physical therapy following botulinum toxin type A injection (odds ratio: 7.82) was the only significant explanatory variable for gait velocity change. Conclusion: Background factors and physical performance at baseline did not affect gait velocity improvement after botulinum toxin type A injection. If botulinum treatment of the ankle plantar flexors in patients with stroke is targeted at walking performance improvement, then physical therapy following botulinum toxin type A injection should be an essential part of the treatment strategy.