Obesity has been previously suggested as an adverse prognostic marker in patients with acute leukemia. To evaluate the relationship between obesity and clinical outcome, disease‐free survival (DFS) and overall survival (OS), in patients with acute myelogenous leukemia (AML), including acute promyelocytic leukemia (APL), we performed a pooled analysis of four CALGB (Alliance) clinical trials. Our study included 446 patients with APL from CALGB 9710, and 1,648 patients between 18 and 60 years of age with non‐APL AML from CALGB 9621, 10503, and 19808. Obesity was defined as BMI ≥30 kg/m². Multivariate Cox proportional‐hazard regression models were fitted for DFS and OS. Obesity was seen in 50% and 38% of APL and non‐APL AML patients, respectively. In APL patients, obesity was associated with worse DFS (HR 1.53, 95% CI 1.03–2.27; P = 0.04) and OS (HR 1.72, 95% CI 1.15–2.58; P = 0.01) after adjusting for age, sex, performance status, race, ethnicity, treatment arm and baseline white blood cell count. Obesity was not significantly associated with DFS or OS in the non‐APL AML patients. In conclusion, our study indicates that obesity has significant prognostic value for DFS and OS in APL patients, but not for non‐APL AML patients. Am. J. Hematol. 91:199–204, 2016. © 2015 Wiley Periodicals, Inc.