Cognitive behavioral therapy (CBT) is an empirically supported treatment for a range of psychological disorders. Theoretically, cognitive change is an important mechanism of CBT that is targeted through cognitive restructuring by clinicians using a variety of treatment techniques throughout therapy. However, less is known about these specific treatment techniques used in CBT packages. Thought records are one of the widely used treatment techniques in CBT to target cognitions by providing a systematic approach to identifying, examining, and changing negative automatic thoughts that arise in emotionally arousing situations.The current study examined the effects of completing a thought record on affective and physiological responses to a laboratory stressor that consisted of a speech task and a mathematical subtraction task (Trier Social Stress Task, TSST; Kirschbaum et al., 1993). Participants were 100 college-students with no history of psychopathology. Prior to preparing for the TSST, participants were randomized to one of two conditions: either a thought record condition (n=50) or a control condition (n=50). Saliva samples were collected and assayed for cortisol, dehydroepiandrosterone (DHEA), and salivary alpha-amylase (sAA) at baseline, post-TSST instruction, immediately following TSST, and 20- and 40-minutes post TSST. Results indicated that the participants in the thought record condition, as compared to those in the control condition, showed greater cortisol response 20-minutes post TSST (peak response). No between group differences were found on DHEA, sAA, affect, or attentional bias.This research provides a novel examination of the causal effects of completing a thought record on physiological responses to a psychosocial stressor in a laboratory study. Overall, results show that completing a thought record impacts physiology (i.e., cortisol). Future research is needed to determine how completing a thought record and other CBT techniques impact affective and physiological responses to stress over time (e.g., over the course of treatment). Overall, this research demonstrates that using experimental laboratory methods can provide additional information to better understand the effective components of CBT.