Previous studies indicate that substance abuse among construction workers is associated with an increased risk of work-related injuries. In fact, using drugs could create a hazard not only for the worker who used them but also for his co-workers; for instance, marijuana can have a significant impact on workers' health, consciousness, performance, absenteeism, and injuries. Since recreational marijuana has been legalized in Colorado and Washington, studying the impact of substance abuse on construction-worker safety has become an important issue. To address this emergent need, this study investigates the advent of safety risks construction workers face due to the legalization of drugs and finds best practices managers can use to mitigate the impact of potential substance abuse. The objective was fulfilled by conducting an online questionnaire and distributing it among safety managers from Colorado and Washington. Participants were asked to summarize relevant safety challenges they faced since the legalization of recreational marijuana and to explain their successful substance-abuse prevention practices. The results of the survey are analyzed and best practices to cope with emerging safety challenges are evaluated. It is expected that the findings reported in this study will provide useful guidelines for safety managers to protect workers from the accidents resulting from substance abuse.