No existing medication has yet been shown to convincingly improve cerebellar ataxia. Therefore, the identification of new drugs for its symptomatic treatment is desirable. The objective of this case series was to evaluate the efficacy of treatment of cerebellar ataxia with the amino acid acetyl-DL-leucine (Tanganil). Thirteen patients (eight males, median age 51 years) with degenerative cerebellar ataxia of different etiologies (SCA1/2, ADCA, AOA, SAOA) were treated with acetyl-DL-leucine (5 g/day) without titration for 1 week. Motor function was evaluated by changes in the Scale for the Rating and Assessment of Ataxia (SARA) and in the Spinocerebellar Ataxia Functional Index (SCAFI) during treatment compared to a baseline examination. Quality of life (EuroQol-5D-3L) and side effects were also assessed. Mean total SARA decreased remarkably (p = 0.002) from a baseline of 16.1 ± 7.1 to 12.8 ± 6.8 (mean ± SD) on medication. There were also significant improvements in sub-scores for gait (p = 0.022), speech (p = 0.007), finger-chase (p = 0.042), nose-finger-test (p = 0.035), rapid-alternating-movements (p = 0.002) and heel-to-shin (p = 0.018). Furthermore, patients showed better performance in the SCAFI consisting of the 8-m-walking-time (8 MW, p = 0.003), 9-Hole-Peg-Test of the dominant hand (9HPTD, p = 0.011) and the PATA rate (p = 0.005). Quality of life increased during treatment (p = 0.003). No side effects were reported. In conclusion, acetyl-DL-leucine significantly improved ataxic symptoms without side effects and therefore showed a good risk-benefit profile. These findings need to be confirmed in placebo-controlled trials.