Trophy-taking in serial homicide—where offenders retain items from victims or crime scenes as keepsakes—is a rare but telling behavior. This chapter examines the psychological underpinnings of trophy-taking through a review of existing literature and original findings from the PRIME model in Gupta and O’Donohue (in progress), which analyzed the role of personality and paraphilic disorders in motivating this behavior. Drawing on data from over 500 serial homicide offenders who operated in the United States, the study found that trophy-taking is significantly associated with antisocial and schizoid personality traits, as well as sexual sadism and necrophilia. The chapter also explores how these findings can inform profiling and investigative strategies, offering practical recommendations and future research directions to improve the understanding and management of high-risk serial offenders.