In 1998, nondisclosure of HIV-status was criminalized in Canada. This in turn has created potential mandatory reporting for psychologists working with persons living with HIV (PLWH) in cases invoking a duty to warn. A brief review of the literature indicates that, at least for some PLWH, this may create a catch-22: While PLWH are aware of the benefits of specific health behaviours (e.g., regular testing, mental health support), feared legal consequences may impede their willingness to access care or disclose their health status. In this space there exists a great opportunity for psychologists to help clients successfully navigate fears, overcome impediments to disclosure, and skillfully manage a legal duty to report. To support psychologists in managing competing ethical and legal duties, this paper presents a comprehensive review of Canadian case law over the past two decades regarding the criminalization of HIV nondisclosure, an overview of the consequences for psychologists of (non-) reporting, and the legal standard for the duty to warn. Additionally, the principles in the Canadian Psychological Association’s Code of Ethics (4th ed.) have been reviewed to inform clinical service in this ethical-legal grey area. Case examples, prompts, and “rules of thumb” are also provided to facilitate group discussion, supervision, and clinical practice in ethical decision-making.