Intrathecal baclofen (ITB) therapy has been proven to reduce severe spasticity in cerebral palsy (CP). However, few results reported the objective gait pattern change after ITB bolus injection in adult ambulatory CP. We therefore evaluated observational and kinematic gait patterns at different ITB bolus injection doses. We performed a test trial of 3-day ITB bolus injections at doses of 12.5 µg, 25 µg, and 50 µg in ambulatory CP. We evaluated modified Ashworth scale, visual analogue scale, observational gait scale, and kinematic gait analysis after ITB bolus injection. Intrathecal administration of low-dose baclofen 25 µg was successfully used not only for the treatment of spasticity but also for the treatment of gait disturbance, whereas the higher dose baclofen 50 µg induced foot drop and deteriorated gait pattern. We experienced dose-dependent changes in gait pattern confirmed by the observational and kinematic gait assessments after ITB bolus injection in adult ambulatory CP.