Background Chronic functional constipation is an epidemic problem in children affects the children's growth. Objectives The aim of this study was to evaluate the growth parameters in children with chronic functional constipation and compare them with healthy individuals. Patients and Methods One hundred children with chronic functional constipation (defined as Rome III criteria) referred to Pediatric Gastroenterology Clinic enrolled in this study. Control group consisted of 100 children who referred for well-child visits, without constipation. Weight, height, body mass index (BMI) and z-score weight, z-score height and z-score BMI were calculated for each patient and control group. Results Both case and control groups consisted of the same age (P = 0.725) and gender (P = 0.777) individuals. The BMI (P < 0.0001) and BMI z-scores (P < 0.0001) of constipated children were significantly higher than the control group. Also, weight (P = 0.004) and weight z-scores (P < 0.0001) were significantly higher in the study group. There was no significant difference in height between the two groups (P = 0.1), but constipated children had higher height z-scores than control group (P = 0.027). The rate of obesity (define as BMI z-score > 2) in children with chronic constipation was 40% that was significantly higher than the normal control group (11%) (P < 0.0001). Conclusions We found a higher obesity rate and also higher BMI and weight z-scores in children with functional constipation compared with healthy control group. The reasons for the association between obesity and constipation are not clear and many factors including diet, activity level, or hormonal influences, are involved that require additional studies.