Recent outbreaks of serogroup C meningococcal disease in Southern California have led the California Department of Public Health to recommend the quadrivalent meningococcal vaccine (MenACWY) for gay, bisexual, and other men who have sex with men (GBMSM) in Southern California. High-risk GBMSM have also been advised to utilize pre-exposure prophylaxis (PrEP) for HIV prevention. Data collected from a community-based sample of HIV-negative GBMSM in Los Angeles County (N = 476) were used in a multinomial logit regression analysis to identify patterns in MenACWY and PrEP usage and evaluate factors associated with use of both, one, or neither of these prevention methods. More than half (56%) of participants had neither been vaccinated nor used PrEP. A smaller percentage (34%) had either been vaccinated or were PrEP users, leaving 10% who had concomitant PrEP and MenACWY use. Higher education, more recent sex partners, illicit drug use, and recent receptive condomless anal sex (CAS) were significantly associated with greater odds of using both prevention methods relative to neither. Higher education, prior sexually transmitted infection diagnosis, more recent sex partners, and recent receptive CAS were significantly associated with greater odds of just PrEP use relative to neither. Higher education was the only factor significantly associated with greater odds of just MenACWY immunization relative to neither. Findings highlight important gaps in immunization among PrEP users and opportunities to screen for PrEP eligibility among GBMSM in conjunction with immunization. Public health practitioners should consider the ways in which strategies to increase PrEP and vaccine-preventable illnesses among GBMSM may complement one another.