Objective: To assess the effect of peritraumatic distress and dissociation on mental health among paramedics and police officers. Methodology: This cross sectional study was conducted in one year from July 2015 to July 2016 in Rawalpindi and Islamabad and included 200 paramedics and 200 police officers from Rawalpindi and Islamabad. We used Peritraumatic Distress Scale, Peritraumatic Dissociation Experiences Questionnaire, and Mental Health Inventory. All instruments were Likert type and had satisfactory reliability and validity. Mental health was measured in term of its positive dimension that is psychological wellbeing. Results: Peritraumatic distress t(198) = 8.13, p<0.001 and peritraumatic dissociation t(198) = 8.11, p<0.001, were higher in police officers (Mean 25.45 8.16 and 22.42 5.96) than paramedics (Mean 17.19 5.91 and 16.61 3.84). Females scored higher on peritraumatic distress t(198) = 2.76, p<0.01, and peritraumatic dissociation t(198)= 2.70, p<0.01 as compared to males. Older employees (i.e., late adulthood) were significantly higher on peritraumatic distress F(2,197) = 10.04, p<0.01. Non -significant dissociation was found on peritraumatic dissociation F(2,197) = 10.04, p>0.05. Conclusion: Peritraumatic distress and dissociation were higher in police officers than paramedics. Females were higher on peritraumatic distress and dissociation compared to males. Peritraumatic distress and dissociation were higher in less in experienced, highly educated and older paramedics and police officers than new, less educated and young paramedics and police officers.