There is a lack of prospective longitudinal studies focusing specifically on the victims exposed to physical violence by a perpetrator other than a family member. To assess the prevalence and comorbidity of post-traumatic stress disorder (PTSD) and anxiety and depression symptoms and the stability of symptoms, in a population of victims of non-domestic physical violence through 8 years. This study had a single group longitudinal design with four repeated measures—the first as soon as possible after the exposure (n = 143 at T1), the second 3 months later (n = 94 at T2), the third after 1 year (n = 73 at T3) and the fourth after 8 years (n = 47 at T4). Questionnaires used were Impact of Event Scale—15 and 22 (IES-15 and 22), Post Traumatic Symptom Scale—10 (PTSS-10) and the Hopkins Symptoms Check List (HSCL-25). Probable PTSD cases measured with IES-15 were 33.6% at T1, 30.9 at T2, 30.1% at T3 (12 months) and 19.1% at T4 (8 years), while probable anxiety and depression cases measured with HSCL-25 were 42.3% at T1, 35.5% at T2, 35.6% at T3 and 23.4% at T4. The estimated probability of recovery from PTSD symptoms during the 8 years is 52%, whereas the corresponding finding concerning anxiety and depression is 43%. The consequences of exposure to physical assault by strangers need to be given more attention as a severe risk of chronic mental health problems.