Noncompliance with prescribed medication has been associated with increased chance of relapse and poor outcome. Side effects may be an important cause of noncompliance. Fifty-one parents of children with acute lymphoblastic leukemia in a tertiary care hospital in Indonesia were interviewed about their perception of side effects and their impact on treatment noncompliance and daily activities. A symptom checklist assessing 13 common symptoms was used to examine side effects. During chemotherapy, childhood acute lymphoblastic leukemia patients suffered from psychological as well as physical side effects. The most frequent side effect reported by parents was behavior alteration (92%). Second and third in frequency were increased appetite and infections, reported by 88% and 83% of parents, respectively. The most severe side effects were leg weakness, increased appetite, and behavior alteration. The overall frequency of side effects was weakly correlated to noncompliance. Reducing the impact of side effects may increase compliance with the treatment.