The goal of this clinical trial is to compare therapist-guided internet delivered prolonged exposure (I-PE) in simple english to a waiting list condition for immigrants in Sweden diagnosed with post-traumatic stress disorder (PTSD). The main objectives are to establish feasibility and preliminary efficacy of I-PE for immigrants with PTSD in a single-blind, parallel-group superiority Randomized Controlled Trial (N=100) comparing I-PE with a waiting-list condition, starting with a nested pilot (N=30) to ensure feasible and acceptable recruitment and treatment strategies. Study participants will be randomly assigned to either eight weeks of I-PE or a waiting-list for the same amount of time on a 1:1 ratio without restriction. Feasibility and acceptability data will be reported including recruitment rate, sample demographics, data attrition, treatment adherence and a detailed dropout analysis. A preliminary investigation of the within-group effect size will also be conducted. Recruitment is designed to be broadly inclusive with minimal exclusion criteria.