Background: Heavy vehicle drivers spend a great deal of time away from their families. This issue and other difficulties around their job may increase risky behaviors among them. The current study aims to investigate the prevalence of opium drugs, stimulants, cannabis, and alcohol use 12 hours before driving among heavy vehicle drivers. Methods: We selected two sites that were in charge of medical examination of drivers and recruited 363 drivers of heavy vehicles (trucks, trailers, and buses). We asked drivers about total number of drivers they knew and number of drivers who experienced use of different types of drugs. The data were analyzed using Network Scale Up Method (NSUM). Findings: Mean of age and job experience was 43.28 ± 10.04 years and 16.07 ± 9.67 years, respectively. The highest and lowest prevalence of drug use related to opium-based drugs at 12.8% to 14.0% and simulants at 1.97% to 2.84%, respectively. The prevalence of alcohol use 12 hours before driving was 4%. Conclusion: 12-hour before driving prevalence of opium-based drugs among drivers was high. This might put them in higher risk of road accidents. There is a need to design appropriate educational programs for them