Objective The purpose of this study was to investigate how locus of control, coping strategies, emotion regulation strategies and social support affect posttraumatic growth. Methods A cross-sectional study design was adopted. A convenience sample of 540 patients with lung cancer was recruited from November 2016 to July 2017 at two tertiary grade A hospitals in China. The participants completed a series of questionnaires. Structural equation modelling was used to explore the effects of psychosocial factors on posttraumatic growth. Results Social support had a direct positive effect on posttraumatic growth (beta = 0.318, SE = 0.071, BC 95% CI = 0.252/0.390), and it also had indirect effects on posttraumatic growth (beta = 0.112, SE = 0.023, BC 95%CI = 0.088/0.135) through mediating psychological factors. Coping strategies and the cognitive reappraisal emotion regulation strategy were the main mediating variables, explaining approximately 73.1% of the indirect effect between social support and posttraumatic growth. Conclusions Our study suggests that Chinese lung cancer survivors can show relatively high posttraumatic growth. There are many mediating paths between social support and posttraumatic growth. These results may help healthcare professionals to identify the psychosocial factors that may benefit lung cancer patients and develop interventions to promote posttraumatic growth.