Idiopathic leg edema is subject to a lot of debates among physicians. Recently sleep apnea was stated to be the cause. We sought to investigate this matter in a sample of Iranian patients with idiopathic leg edema. In this case-control study, 110 patients were selected based on our inclusion/exclusion criteria and allocated to the case (with idiopathic edema, n=55) and control (without edema, n=55) groups. Sex, age, weight, height, and body mass index (BMI) of all subjects were recorded. We evaluated daytime somnolence of all patients using Epworth sleepiness scale and then calculated Apnea, hypopnea index (AHI) using ResMed ApneaLink and AHI≥15 were considered as sleep apnea. Age and sex of both groups were not significantly different. Cases had higher BMI than control groups (P=0.03), but they were not significantly different for obesity (P=0.197). AHI was significantly higher in cases (17.85±24.31 vs. 9±7.37 P=0.012). Daytime somnolence (cases 8.18±5.3 vs. controls 6.5±3.3) was also higher in cases. Overall Odds ratio of leg edema and sleep apnea was 3.068 (P=0.025), but it wasn't significant in the two genders. Idiopathic bilateral leg edema is strongly associated with sleep apnea. Routine sleep apnea assessment in patients with idiopathic bilateral leg edema is recommended for both genders.