While prison needle exchange programs, or prison needle and syringe programs, have existed in different parts of the world since the 1990s, little is known about how currently incarcerated people perceive them—particularly in Canada, where such programs have only recently been implemented. This study explores incarcerated women's perceptions of a recently implemented prison needle exchange program using in-depth, semi-structured qualitative interviews with 56 federally incarcerated women in Western Canada. In particular, we explore the barriers that women perceive in accessing the prison needle exchange program. These perceived barriers contributed to our participants’ negative views of the prison needle exchange program as well as their overwhelming lack of support for its implementation. Our participants felt that the prison needle exchange program acts as an obstacle to sobriety and could increase different types of harm—including encouraging injection drug use and contributing to overdoses—within the prison. Participants also identified other barriers to using the prison needle exchange program, including a perceived lack of confidentiality/anonymity for users of the program and that the prison needle exchange program itself is structurally incompatible with the rules and operations of a prison system that continues to criminalize drugs. Using an implementation science framework, we argue that this situation accentuates the need for significant consultations with incarcerated people about the operation of such programs, and for funds to support other programs that target participant-identified root causes of substance misuse, such as programs that address past trauma and victimization. At the same time, we caution that some barriers may be inherent in how prisons are structured.