Background Multimorbidity is both an individual and societal problem. For society, patients with multimorbidity increase healthcare costs. For the individual, living with multimorbidity is complex, and there is an inverse relationship between a patient's Quality of Life (QoL) and their number of chronic conditions. Numerous intervention studies target these problems, yet there is no multimorbidity-specific patient-reported outcome measure (PROM) developed specifically for this group with adequate measurement properties to assess QoL. This study explores what overall needs regarding QoL are affected by living with multimorbidity through qualitative interviews. With this, we conceptualise Needs-based QoL specifically for this group, ensuring high content validity (regarding relevance and comprehensiveness) of using the Needs-based approach to measure their QoL. This is essential as this preliminary study leads to the development of the MultiMorbidity Questionnaire (MMQ), a PROM measuring QoL among patients with multimorbidity. Methods This study draws upon qualitative interviews with fifteen patients with multimorbidity based on a semi-structured interview guide following the Needs-based approach. This approach allowed the patients to cover needs relevant for their QoL in relation to the complexities of living with multimorbidity. The transcribed interviews were thematically analysed, inspired by Braun and Clarke's reflexive approach. Results Analysis of the interviews resulted in the construction of six intertwined domains relevant to patients with multimorbidity, covering their Needs-based QoL; "Physical ability", "Self-determination", "Security", "Partner and social life", "Self-image", and "Personal finances". "Physical limitations" and "Personal finances" were stated as core needs implicating the other domains. Conclusion This study shows six intertwined overall domains relevant for patients with multimorbidity regarding their Needs-based QoL; "Physical ability", "Self-determination", "Security", "Partner and social life", "Self-image", and "Personal finances". These needs are relevant in a Danish context, with a generally high standard of living. Based on this conceptual framework of Need-based QoL for patients with multimorbidity, we will develop items for a new patient-reported outcome measure called the MMQ.