Research on patient engagement in health care shows that better health outcomes and lower healthcare costs are observed among highly engaged patients. Similar to other illnesses, high levels of patient engagement in HIV care are considered essential to maintaining optimal health, and patients who are on treatment and retained in HIV care are known to have better health outcomes. In this article, we draw on focus group discussion data with patients living with HIV in order to explain tacit expectations associated with engagement in care. The main objective of our research was to elicit an explanatory model of engagement in HIV care from the patients' perspective. We conducted focus group discussions with a sample of two distinct types of patients: those who regularly attended medical appointments and those who did not. In total, we conducted six focus group discussions (n = 43) across in three cities in the US; these included two focus group discussions with a well-engaged and less-well-engaged group in each location. Both types of patients assigned a moral dimension to engagement in care, in that well-engaged patients were considered to be 'good' patients. Aspiring to become a 'good' patient provided a meaningful goal for some and deepened vulnerabilities among patients that struggled to achieve this status. More vulnerable patients may feel less secure in health care interactions and these feelings may be amplified if patients have an unreasonable impression of what constitutes a 'good' patient; thereby leading to disengagement in care. Our findings can inform the development of patient-centered, tailored messages to better serve patients struggling to stay engaged in HIV care.