Children with cancer undergo many invasive medical procedures that are often painful and highly distressing, including bone marrow aspiration (BMA) and lumbar puncture (LP). Psychosocial interventions have been demonstrated to reduce children's distress resulting from invasive medical procedures. The aim of the study is to assess the efficacy of psychosocial interventions to reduce distress in children with cancer undergoing BMA and LP in a pediatric cancer center in Taiwan. Children with cancer who received treatment between March 2015 and December 2016 at Chang Gung Memorial Hospital, Linkou, Taiwan were eligible for the study. The psychosocial intervention comprised preparation and cognitive behavioral intervention and was provided by a certified child life specialist. The assessment instrument was the revised version of the Observational Scale of Behavioral Distress (OSBD-R). The behavioral distress of patients who underwent psychosocial interventions for BMA and LP was compared with patients without interventions. We also analyzed the difference of behavioral distress in patients' pre- and post-psychosocial intervention for BMA and LP. Eighteen patients were enrolled into this study. The mean age of diagnosis of leukemia was 6.6 years old (range: 3-11 years). Fifteen patients were diagnosed with acute lymphoblastic leukemia, and 3 were diagnosed with acute myeloid leukemia. The mean of OSBD-R total scores in 7 patients with psychosocial intervention was significantly lower than the mean score in 6 patients without intervention (0.65 vs. 4.81, p = 0.002). Pre- and post-psychosocial intervention for BMA and LP behavioral distress were evaluated for the remaining 5 patients. Consistently, there was a significant reduction of the OSBD-R score following interventions (3.04 vs. 7.81, p = 0.025). Psychosocial interventions provided by a certified child life specialist have a significant potential to reduce children's distress during BMA and LP in pediatric healthcare settings in Taiwan.