ABSTRACT Background Multimorbidity—coexistence of two or more chronic conditions in the same individual—is a growing global healthcare challenge. Despite recognition of the difficulties in managing multimorbidity, there is a limited understanding of lived experiences and care improvement priorities as identified by key stakeholders. Objectives The study aimed to explore lived experiences of patients with multimorbidity, their family caregivers, and interprofessional healthcare workers, and to identify shared care improvement priorities. These findings were synthesized into a multimorbidity management toolkit. Methods An experience‐based co‐design study with six stages was implemented, considering human‐centered design. Participants included patients aged 50 years and above living with heart failure and multimorbidity, family caregivers, and multidisciplinary healthcare professionals recruited in Maryland, USA. Following study preparation and ethical approval (Stage 1), in‐depth individual interviews (Stages 2 and 3) were conducted, and the results were discussed during co‐design events and working group meetings (Stages 4 and 5) to reach a consensus on care priorities and specific strategies. The study findings were summarized into a multimorbidity management toolkit that was shared with participants at a celebration event (Stage 6). Data analysis included descriptive statistics and inductive thematic methods. Results Forty‐six individual interviews were conducted: 24 patients (mean ± SD age 71 ± 9 years; 54% women; with an average of 8 morbidities), 7 family caregivers (mean ± SD age 64 ± 14 years; 57% women), and 15 healthcare professionals (mean ± SD age 36 ± 10 years). A total of 18 participants attended two co‐design events. Multiple working group meetings were organized to receive diverse input. Four shared care improvement priorities emerged: (1) communication, (2) care coordination and follow‐up care, (3) mental and emotional support, and (4) health education for patients and caregivers. Conclusion Person‐centered care models that emphasize shared strategies to improve communication, care coordination, education, and emotional support, as outlined in the toolkit, may enhance multimorbidity management and patient outcomes.