Social prescribing has gained attention internationally as a health-promoting way to address patients’ nonmedical needs, yet research in the Nordic healthcare context remains limited. This theory-informed process evaluation set out to unpack the early implementation of a social prescribing model in Swedish primary care, developed to reduce loneliness and promote health among older adults. Guided by Normalization Process Theory (NPT) and the Consolidated Framework for Implementation Research (CFIR), this study assessed how and under what conditions the model was implemented across 10 primary care centres between May 2023 and December 2024. Data were triangulated from interviews with prescribers and patients, alongside prescribing and follow-up materials. Thematic analysis indicated that while the approach was perceived as relevant and timely, implementation was hindered by a selective use of the routine screening question and lack of person-centredness in the prescribing process, reflecting poor fidelity to core principles. Leadership engagement and managerial support that appeared symbolic rather than active further constrained implementation by limiting integration into organizational workflows, rendering the approach peripheral or optional to other clinical and statutory tasks. The model’s operationalization also lacked alignment with community resources and bridging structures, limiting implementation by failing to meet patients’ needs and expectations. While the Swedish social prescribing approach aligns with national policy discourse and prescribers’ values, its scale-up will require clearer guidance on components needing high-fidelity delivery, necessary organizational structures, accessible local resources, and mechanisms linking primary care with the wider community. These findings contribute to the international evidence base on social prescribing and inform refinements of the Swedish model.