Sensory processing sensitivity (SPS) relates to individuals' sensitivity to stimuli and their emotional responses to adversity. SPS was found to be associated with a variety of stress-related disorders, however, little is known about the relationship between SPS and posttraumatic stress symptoms (PTSS). The current study aimed to examine interaction effects between SPS and early PTSS assessed daily during the first week after a motor vehicle collision on subsequent 1- and 4-months PTSS. Participants (N = 70; 38 [54.3%] women, aged 18–63) were screened and recruited during an Emergency Department visit following motor vehicle collisions. Online questionnaires included baseline SPS, early PTSS assessed daily on days 2–6 post-hospital visit, and follow-up 1- and 4-months PTSS. Linear regression analyses showed positive correlations between SPS and both follow-up PTSS, however, after controlling for early PTSS, SPS was not directly associated with PTSS at either follow-up. SPS also negatively moderated the association between early PTSS and 1-month PTSS. SPS could potentially exacerbate early stress symptoms, which may further develop into lasting PTSD symptomatology. Identifying core characteristics of SPS associated with increased early stress reactions could assist in targeting people at risk that might benefit from early interventions following adverse events. [ABSTRACT FROM AUTHOR]