Background: Malnutrition and sarcopenia impact the physical health and quality of life of community-dwelling older adults. Managing these conditions requires integrating nutritional and exercise interventions delivered by professionals from diverse backgrounds. Interprofessional collaboration holds promise for providing integrated, person-centered care to older adults. However, to tailor such care, it is essential to understand the needs and wishes of older adults, which remain underexplored. This study aimed to understand the needs and wishes of community-dwelling older adults regarding interprofessional treatment for (risk of) malnutrition and sarcopenia. Methods: We conducted a grounded theory study. Data collection involved semi-structured interviews and focus groups with community-dwelling older adults who are undergoing treatment or have been treated for (risk of) malnutrition and/or sarcopenia. We systematically analyzed the data using open, axial, and selective coding and developed a conceptual model. Results: Interviews and focus groups were conducted with 18 older adults. Three selective codes were identified: 1) older adults need to be involved in their interprofessional treatment, 2) older adults need healthcare professionals to be well-informed about their interprofessional treatment, and 3) older adults need collaboration amongst involved healthcare professionals in interprofessional treatment. Our conceptual model addresses the needs and wishes of older adults in relation to interprofessional collaboration. Older adults’ needs highlight what is missing, while their wishes offer ways to fulfill these needs. Conclusion: Older adults’ need for involvement in interprofessional treatment can be met by engaging them actively in healthcare decisions and as partners to healthcare professionals. The need for well-informed healthcare professionals can be fulfilled by ensuring accessible healthcare information, the prevention of conflicting advice, and the prevention of repeating medical history. Finally, the need for collaboration among healthcare professionals can be fulfilled by healthcare professionals communicating openly and directly and working closely together.