A diagnosis of young-onset dementia (YOD) is a life-altering event for both persons with dementia and their spousal caregivers. Dyadic coping (DC) theoretical models acknowledge that dyads cope with stressors as a unit, but these models have yet to be used in YOD. To explore the lived experiences of couples managing YOD using an integrated DC model. This qualitative study recruited couples from a single major medical setting and through social media. Eligibility criteria included cohabitation, 1 partner diagnosed with YOD and able to participate, and both partners willing to participate. Live online video interviews were conducted from March to June 2020. One semistructured interview, which was recorded and subsequently transcribed. Recruitment was stopped once thematic saturation was reached. Five themes were deductively derived based on the integrated DC framework, including stress communication, positive individual DC, positive conjoint DC, negative individual DC, and negative conjoint DC. Within each theme, subthemes were inductively identified to further characterize couples' dyadic coping experiences with YOD. A total of 23 couples were interviewed, comprising persons with dementia (11 women [48%]; mean [SD] age, 61.3 [4.65] years; mean [SD] time from diagnosis, 3.11 [3.85]) years; and spousal caregivers (13 women [57%]; mean [SD] age, 60.5 [5.40] years). Data supported the 5 a priori DC themes and novel subthemes describing couples' experiences with YOD. Specifically, couples enacted positive conjoint DC by approaching challenges using a teamwork approach to problem solving and relying on collaborative communication. In contrast, couples engaged in negative conjoint DC through mutual avoidance, leading to increased negative communication and conflict. Couples described initially engaging in avoidance and withdrawal to navigate YOD-related stressors. While these strategies provided short-term relief from challenging emotions, they prevented engagement in adaptive coping (eg, acceptance and collaborative problem-solving) to promote long-term adjustment. This study used an evidence-based integrated DC approach to identify the positive and negative coping behaviors of couples managing YOD. To our knowledge, this is the first study to use a DC framework to guide qualitative analysis, and it provides valuable insights into DC strategies used by couples navigating YOD-related stressors. Findings can inform the development of dyadic psychosocial services for couples managing YOD and have implications for other progressive illnesses.