Background: Younger women with chronic disease (<60 years of age), especially women with stereotypically "men's" heart disease (HD), are understudied. Unique difficulties may occur with HD, which is less commonly associated with women, compared with breast cancer (BC). Similarities may also exist across younger women, as chronic disease is less normative in younger people. Intersections of gender, age, and the specific disease experience require greater attention for improving women's health. This exploratory qualitative study compared younger women's experiences of HD or BC. Methods: Semistructured interviews with 20 women (n = 10 per disease) were analyzed using applied thematic analysis. Results: Amidst building careers, intimate relationships, and families, women felt thwarted by disease-related functional problems. Cognitive-behavioral coping strategies spurred resilience, including integrating the illness experience with self-identity. Barriers arose when medical professionals used representativeness heuristics (e.g., chronic disease occurs in older age). Important experiences in HD included worsened self-image from disability, negative impact of illness invisibility, and persisting isolation from lacking peer availability. Initial medical care reported by women with HD may reflect gender biases (e.g., HD missed in emergency settings and initial diagnostics). New information provided by the younger women includes limited illness-related optimism in women with HD facing age and gender stereotypes, as well as the advantages and disadvantages of peer availability in BC. Conclusions: Greater public awareness of younger women with chronic disease, alongside structural support and connection with similarly challenged peers, is suggested. As advocacy for BC awareness and action has strengthened over past decades, similar efforts are needed for younger women with HD.