Objective: Explore trauma, stress and other predictive factors for treatment outcome in Conversion Disorder/functional neurological disorder (CD/FND). Methods: Prospective observational design. Clinical cohort study amongst consecutive outpatients with DSM-IV CD/FND in a specialised mental health institution for Somatic Symptom Disorders and Related Disorders (SSRD), presented between 1/2/2010 and 31/12/2017. Patient files were assessed for early childhood trauma, childhood sexual abuse, current stress and other predictive factors. Patient Related Routine Outcome Monitoring (PROM) data were evaluated for treatment outcome at physical(Patient Health Questionnaire [PHQ15], Physical Symptoms Questionnaire [PSQ]) level as primary outcome, and depression (Patient Health Questionnaire[PHQ9]), anxiety (General Anxiety Disorder[GAD7]), general functioning (Short Form 36 Health Survey[SF36]) and pain (Brief Pain Inventory [BPI]) as secondary outcome. Results: 64 outpatients were included in the study. 70.3% of the sample reported childhood trauma and 64.1% a recent life event. Mean scores of patients proceeding to treatment improved. Sexual abuse in childhood (F (1, 28) =30.068, β = .608 p<.001) was significantly associated with worse physical (PHQ15, PSQ) treatment outcome. 42.2% reported comorbid depression, and this was significantly associated with worse concomitant depressive(PHQ9) (F[1,39] =11.526, β = .478, p=.002) and anxiety(GAD7)(F[1,34]= 7.950, β = .435, p = .008) outcome. Conclusion: Childhood sexual abuse is significantly associated with poor treatment outcome in CD/FND. Randomised Clinical Trials evaluating treatment models addressing childhood sexual abuse in CD are needed.