Previous trials have demonstrated that Written Exposure Therapy (WET) is effective in treating post-traumatic stress disorder (PTSD), achieving comparable outcomes to more time-intensive treatments such as prolonged exposure and cognitive processing therapy, but with lower dropout rates. Its short duration, absence of between-session homework, and high adherence rates make WET a promising alternative to traditional more time-intensive therapy. Despite established efficacy of WET in controlled trials, questions remain about its feasibility, tolerability, and flexibility when implemented in routine psychiatric outpatient settings. This study addresses these gaps. Twenty-four patients, most with moderate to severe PTSD and significant psychiatric comorbidities, were recruited from a specialised psychiatric outpatient clinic for PTSD and underwent WET over a five-to-six-week period. Feasibility was assessed in terms of adherence, client satisfaction, adverse events, effectiveness, time requirements, and flexibility. PTSD symptom severity was measured at baseline, post-treatment, and one-month follow-up using the PTSD Checklist for DSM-5. The treatment was delivered either through face-to-face sessions at the clinic ( = 7) or via video conferencing ( = 15), with two participants receiving a combination of formats. Adherence was high, with 23 of 24 participants completed treatment. Client satisfaction was excellent, with a mean score of 25.91 (SD = 4.27) on the Client Satisfaction Questionnaire. Average therapist time required was under six hours per patient. Within-group analyses showed significant reductions in PTSD symptoms at one-month follow-up  = 1.08, 95% CI: 0.47-1.69). No serious adverse events were reported. WET was feasible, resource-efficient, video-compatible, and suitable for delivery by individual therapists with limited training. WET proved to be a feasible, effective, and resource-efficient intervention for PTSD in routine psychiatric care. Its implementation may expand access to evidence-based treatment and reduce reliance on full-dose CBT. Further research should explore its role in optimising care pathways and addressing waiting lists. ClinicalTrials.gov identifier: NCT04328935.