Weight gain is often observed in children with acute lymphoblastic leukemia (ALL) who undergo chemotherapy including steroids. An increase in body mass index (BMI)-standard deviation score (SDS) during induction therapy is reported as a risk factor for obesity after treatment. However, risk factors of an increase in BMI-SDS during induction therapy are not known. Ninety-six patients with ALL who were treated at our hospital between 1996 January and September 2013 were analyzed retrospectively. Daily body weight measurement was initiated in July 2005 in an attempt to control weight. Fifty-four patients were boys and 42 were girls. The median age at onset was 5.1 years (0.5–16.6 y), and 7.3% of patients were overweight/obese at onset. BMI-SDS increased +0.1% (−3.3% to +3.2%) during induction therapy. BMI-SDS increased by 1 and 2 or more SDs in 20% and 3% of patients, respectively. In multivariate analysis, non–high-risk treatment and earlier treatment start date (before daily body weight measurement) were independent risk factors. Ten percent of patients were overweight/obese at 3 years after completion therapy, and high BMI-SDS after induction therapy was a risk factor. Daily body weight measurement might prevent excess weight gain during induction therapy, resulting in patients maintaining a healthy weight after ALL treatment.