Background Post-traumatic growth (PTG) refers to beneficial psychological change following trauma. Aims This study explores the sociodemographic, health and deployment-related factors associated with PTG in serving/ex-serving UK armed forces personnel deployed to military operations in Iraq or Afghanistan. Method Multinomial logistic regression analyses were applied to retrospective questionnaire data collected 2014-2016, stratified by gender. PTG scores were split into tertiles of no/very low PTG, low PTG and moderate/large PTG. Results A total of 1447/4610 male personnel (30.8%) and 198/570 female personnel (34.8%) reported moderate/large PTG. Male personnel were more likely to report moderate/large PTG compared with no/very low PTG if they reported a greater belief of being in serious danger (relative risk ratio (RRR) 2.47, 95% CI 1.68-3.64), were a reservist (RRR 2.37, 95% CI 1.80-3.11), reported good/excellent general health (fair/poor general health: RRR 0.33, 95% CI 0.24-0.46), a greater number of combat experiences, less alcohol use, better mental health, were of lower rank or were younger. Female personnel were more likely to report moderate/large PTG if they were single (in a relationship: RRR 0.40, 95% CI 0.22-0.74), had left military service (RRR 2.34, 95% CI 1.31-4.17), reported better mental health (common mental disorder: RRR 0.37, 95% CI 0.17-0.84), were a reservist, reported a greater number of combat experiences or were younger. Post-traumatic stress disorder had a curvilinear relationship with PTG. Conclusions A moderate/large degree of PTG among the UK armed forces is associated with mostly positive health experiences, except for post-traumatic stress disorder.