Abstract: Objective: This article presents a randomized waitlist-controlled trial testing Couple HOPES, a coach-guided, online intervention for couples wherein one member had posttraumatic stress disorder (PTSD) symptoms. Aims involved examining whether Couple HOPES resulted in greater improvements in PTSD symptoms, relationship satisfaction, and secondary outcomes compared to a waitlist, whether outcomes were maintained over a 3-month follow-up, and whether outcomes differed if PTSD was COVID-19-related. Method: Sixty-seven couples were recruited, where one partner met criteria for likely PTSD and was either a military member, veteran, first responder, health care worker, and/or whose PTSD symptoms were related to COVID. Couples were randomized to receive Couple HOPES immediately or after 8 weeks. Outcomes were measured at the beginning, middle, and end of Couple HOPES/the waiting period, and 1- and 3-months after Couple HOPES. Measures of PTSD and relationship satisfaction were also completed during each of seven modules. Results: Intent-to-treat analyses showed greater improvements in self- and informant-reported PTSD in those receiving Couple HOPES relative to waiting, with large- and medium-effect sizes, respectively. Partners without PTSD symptoms reported greater improvements in relationship satisfaction in Couple HOPES compared to the waitlist with a small effect size, but people with PTSD symptoms did not. Uncontrolled follow-up showed reversion of gains in some outcomes. Whether PTSD was COVID-19-related did not significantly moderate outcomes. Conclusions: Findings support the efficacy of this low-cost, scalable intervention for improving PTSD, regardless of the means through which it was acquired (COVID-19-related or not). Further testing with larger sample sizes is needed.