Sexual homicide has been heavily studied, yet the majority of the studies have focused on male offenders killing female victims (MFSH), thereby neglecting male-on-male sexual homicide (MMSH), i.e., instances where an adult male offender murders an adult male victim. To summarize the current understanding of this crime type, a systematic review was conducted. The objective was to provide a clearer picture of MMSH, e.g., how common it is, its modus operandi (i.e., offending pattern), and demographic characteristics of victims and the offenders. Following PRISMA (2009) guidelines, a thorough search of four databases (PsychInfo, PubMed, Web of Science and ScienceDirect) was conducted yielding a total of 165 records. After an in-depth record screening (excluding duplicates and records written in non-English language) 116 records remained. Following a second screening process a total of four fulltext empirical articles were eligible for inclusions. The summation of the studies suggests that; MMSH remains a low base rate phenomenon, that motivational differences and a new three-type classification are present within this group, and that differences in offending patterns also exist between MMSH and MFSH. Today’s research collectively supports the presence of a suggestive heterogeneity both within MMSH but also within sexual homicide in general.