In this study, the objective was to assess the occurrence of specific vulnerability factors among adult and adolescent females attending a Norwegian sexual assault center (SAC). We also explored assault characteristics and investigated whether these characteristics differed between the group of patients with vulnerability factors compared with the group without such factors. We conducted a retrospective descriptive study of 573 women ≥ 12 years of age attending the SAC at St. Olavs Hospital, Trondheim, Norway, between July 1, 2003 and December 31, 2010. A patient was considered vulnerable if at least one of the following features was present: intellectual or physical disability; history of present/former mental health problems; history of present/former alcohol/substance abuse; or former sexual assault. At least one vulnerability factor was present in 59% of the cases. More than one vulnerability factor was present in 29%. Reporting at least one vulnerability factor was associated with a higher patient age, unemployment, a higher frequency of reported light/moderate physical violence, and the documentation of minor body injury. In contrast, those without vulnerability more often were students assaulted during night time, by a casual or stranger assailant and reporting a higher intake of alcohol prior to the assault. There are obvious patterns of differences in the nature of sexual assaults reported among victims with specific vulnerability factors compared with victims without these factors. Future research should address these differences and possible solutions for better protection of especially vulnerable individuals against sexual offenses, such as those with mental health and substance abuse difficulties.