IntroductionInjectable opioid agonist treatment (iOAT) is an evidence-based treatment that serves an important minority of people with opioid use disorder who require specialized care. Unique to iOAT care is the consistency with which clients access treatment (up to three times daily), a condition that creates repeated opportunities for health care engagement. To date, no study has examined therapeutic relationships in this life saving, nurse-led treatment that can have lasting implications in the equitable delivery of other forms of addictions care. MethodsThis study used grounded theory to generate a dynamic framework for therapeutic relationship building in iOAT. Researchers collected semi-structured interviews from registered nurses working in iOAT sites (n=24) form January 2020 through June 2022. The study analyzed collected data through a constant comparative analysis; explored through open, axial, and selective coding; and assessed in a conditional relationship matrix. The team reviewed key findings with stakeholders through formalized processes of engagement to confirm saturation of coding categories. Throughout data collection and analysis, researchers integrated feedback from additional knowledge users and member checking. Reported findings adhered to the COREQ1 standardized checklist. ResultsWe identified five interrelated categories that created a distinct culture of care for iOAT nurses: Ways of Knowing, Personal Investment, Leveraging Empathy, Finding Flexibility, and Collaborating to Overcome. Through creating a safe, nonjudgmental environment, nurses establish therapeutic relationships that build trust to identify client needs outside of medication administration. In turn, nurses participate in team-based problem solving to advocate for client needs. If nurses cannot find flexibility within and outside of the health care system to improve client engagement, tensions can arise and therapeutic relationships can be strained. ConclusionsTherapeutic relationships are an integral part of building and maintaining trust with a population that has been precariously involved with other forms of health care. Nurses make a substantial effort to create a safe and nonjudgmental environment to manifest a culture of care that bridges client needs and program access. Without the expansion of access to iOAT programs and their embedded services, nurses are limited in their ability to provide individualized care for clients with diverse needs.