The relation of aspects of rest–activity patterns, i.e., social zeitgebers, physical activity and circadian rhythm, to the severity of PTSD and depressive symptoms has not previously been studied. Doing so could provide valuable insight into possible targets for treatment. Our study explored these links in a population of 219 trauma-affected refugees diagnosed with PTSD who were seeking treatment. Data regarding social zeitgebers, such as affiliation with the labor market and contact with social network, and symptoms of PTSD and depression were collected from them. Furthermore, their levels of physical activity and circadian rest–activity parameters were calculated from actigraphy data. Bivariate correlation analyses and multiple linear regression analyses were performed to examine various aspects of rest–activity regarding relation to severity of PTSD and depressive symptoms. Several social zeitgebers were associated with severity of PTSD and depressive symptoms. The level of physical activity was unrelated to symptom severity, whereas a rest–activity pattern, with early onset of the most active 10 h, was associated with severity of PTSD, and a circadian rhythm with a large difference between periods of rest and activity was associated with severity of depression. Social zeitgebers, levels of physical activity and circadian rhythm parameters were all associated with each other. Social zeitgebers and circadian rhythm parameters were significantly related to the severity of PTSD and depressive symptoms—a relationship indicating that interventions targeting regularity of daily routines have a potential role in treating PTSD and depression in trauma-affected refugees. Trial registration: ClinicalTrials.gov, ID: NCT02761161, April 27, 2016.