Firearm availability is correlated with increased suicide mortality. Some firearm owners may be more vulnerable to suicide than others, but heterogeneity among firearm owners has received little empirical attention. The present study used latent class analysis (LCA) to identify subgroups of firearm owners who keep firearms primarily for protection (i.e., protective firearm owners) in a national sample of 2311 U.S. adult firearm owners. Self-protection was the primary motive for firearm ownership for 1135 (49.1%) participants. Results of the LCA identified three latent classes that differed with respect to secondary reasons for firearm ownership, number and types of firearms owned, firearm ownership history, and demographics. The smallest latent class (n = 26, 2.3% of protective firearm owners), which owned a high volume of firearms and had high levels of early childhood exposure to firearms, reported significantly higher rates of lifetime preparatory suicidal behaviors. Results suggest that firearm owners are a heterogeneous population, with some subgroups being more vulnerable to suicide than others.