“Doomsday prepping” is a phenomenon which involves preparing for feared societal collapse by stockpiling resources and readying for self-sufficiency. While doomsday prepping has traditionally been reported in the context of extremists, during the COVID-19 pandemic, excessive stockpiling leading to supply shortages has been reported globally. It is unclear what psychological or demographic factors are associated with this stockpiling. This study investigated doomsday prepping beliefs and behaviors in relation to COVID-19 proximity, demographics, coping strategies, psychopathology, intolerance of uncertainty (IU), and personality in 384 participants (249 female) in an online study. Participants completed a number of questionnaires including the Post-Apocalyptic and Doomsday Prepping Beliefs Scale and a scale designed for the current study to measure prepping in the context of COVID-19. These were analyzed using ANOVAs, correlational, and mediation analyses to examine relationships between psychometric variables and stockpiling. Prepping beliefs and behaviors were higher in males than females and positively associated with anxiety, obsessive-compulsive symptoms, IU, and traditional masculinity traits. Older age, male gender, obsessive-compulsive symptoms, and traditional masculinity predicted unique variance in prepping. The relationship between gender and stockpiling was mediated by social learning (witnessing other people panic buying) and the perceived threat of COVID-19 (doomsday interpretations) while proximity and personal vulnerability to COVID-19 were non-significant. Results indicate that panic buying was influenced more by witnessing others stockpiling, personality, and catastrophic thinking rather than by proximity to danger. Education could target these factors in ongoing waves of the pandemic or future catastrophes.