Private security guards occupy an increasingly prominent role in the policing of private and public spaces. There are growing concerns regarding security guards' potential to shape violence, discrimination, and adverse health outcomes among vulnerable populations, including people who use drugs (PWUD). This is relevant in Vancouver, Canada, where private security guards have increasingly been employed by private organizations to manage public and private spaces, including those within urban drug scenes. This qualitative study sought to understand interactions between PWUD and private security guards and explore their impacts on health care access, risks, and harms among PWUD. Semi-structured interviews were conducted with 30 PWUD recruited from two ongoing prospective cohort studies. Interviews were transcribed and analyzed using a coding framework comprised of a priori and emergent categories. Study data indicate that participants experience pervasive, discriminatory profiling and surveillance by security guards, which exacerbates existing social marginalization and structural vulnerability, particularly among PWUD of Aboriginal ancestry. Participants reported that security guards restrict PWUD's access to public and private spaces, including pharmacies and hospitals. PWUD also reported that their interactions with security guards often involved interpersonal violence and aggression, experiences that served to increase their vulnerability to subsequent risks and harms. Our findings highlight that private security forces contribute significantly to the everyday violence experienced by PWUD within drug scenes and elsewhere and do so in a manner very similar to that of traditional police forces. These findings point to the urgent need for greater oversight and training of private security guards in order to protect the health and safety of PWUD.