Rejection of new anti-SARS-CoV-2 booster doses among immunosuppressed and elderly individuals may be a concern, especially as the intention to vaccinate does not always translate into actual behavior. Few studies have addressed this issue in people living with HIV (PWH). We investigated attitudes of PWH toward SARS-CoV-2 vaccination, focusing on factors associated with noncompliance with additional vaccine doses (AVDs, 4th and 5th). We analyzed participants of the prospective observational HIV-VAC study conducted at the National Institute for Infectious Diseases “L. Spallanzani” IRCCS, Rome (September 2022–June 2023). Eligible patients with complete vaccination schedules were voluntarily recruited and completed a 13-item survey on demographics and vaccination attitudes. Multivariate logistic regression was used to describe the relationship between “compliant” vs. “non-compliant” groups. Of 316 participants, 240 (75.9%) were compliant and 76 (24.1%) non-compliant. Compliance was 70% for the fourth and 30% for the fifth dose; noncompliance was 19.9% and 4.1%, respectively. Older age (p = .012) and information from non-institutional sources (p < .0001) were associated with higher noncompliance. Among non-compliant participants, 34.4% reported concerns about side effects. In PWH aged >50, fear of side effects and reliance on unofficial information sources are major barriers to AVD uptake. Non-compliant individuals tend to persist in their refusal over time. Tailored communication and healthcare professional training are crucial to improve vaccine adherence, and further multicenter studies are warranted.