Time monitoring behavior (TMB) commonly occurs among insomnia patients, often leads to frustration about sleeplessness, and perpetuates insomnia symptoms. Few studies have explored relationships between time monitoring and insomnia, and none have studied the potential relationships between insomnia, TMB, and posttraumatic stress symptoms (PSSs). In this retrospective chart review of 1078 patients seeking care at a sleep medical center, the patients presented with one of three chief sleep complaints (poor sleep quality, 51%; sleep-disordered breathing, 26%; and insomnia, 24%), and 32% reported moderate to severe PSSs. Both insomnia and time monitoring severity were greater in the 350 patients with PSSs compared with the 728 patients with minimal or no such symptoms. Insomnia and time monitoring severity correlated significantly with total posttraumatic stress scores and most strongly with the arousal subscale. Research on interventions to treat TMB may inform relationships between insomnia and posttraumatic stress.