Background <p>Despite the importance of promoting healthy lifestyles in primary healthcare (PHC) to prevent non-communicable diseases, implementing and sustaining evidence-based health-promotion lifestyle practices remains challenging. This study aimed to evaluate the sustainability of uptake of a health-promoting practice using a 12-month multifaceted implementation intervention in a Swedish PHC setting.</p> Methods <p>A non-randomized parallel group design was used to compare five PHC intervention centers and five matched control centers with respect to health-promotion activities registered in medical records at: 6 months pre-implementation, during a 12-month implementation phase, and a follow-up at 18 months (sustainability). The intervention centers received a multifaceted implementation intervention based on a leadership change model using internal and external facilitators. Uptake was analysed using negative binomial mixed-effects models with a log link, modelling monthly uptake rates with an offset for the number of visits. Time since intervention initiation and time since the post-implementation phase were modelled using restricted cubic splines, allowing intervention effects to vary over time. Models were adjusted for seasonality, secular trends, patient sex, and site pair, with site included as a random effect. Intervention effects were estimated as ratios of rate ratios with simultaneous 95% confidence intervals.</p> Results <p>The intervention centers successfully adopted and sustained the clinical intervention. At the 18-month follow-up, intervention centers sent out 7.2 times as many lifestyle screening forms compared with the control centers. The mean crude uptake difference was 43.6 and the relative rate was estimated at 2.23, indicating that patients at the intervention centers were more often asked about their lifestyle and more often received advice or consultative conversations about lifestyle changes.</p> Conclusions <p>This multifaceted implementation intervention, focusing on leading change and facilitation in a routine clinical setting, increased the uptake of a health-promoting practice at the PHC intervention centers that was sustained over time. Health-promoting activities reached a larger proportion of patients in the intervention centers, indicating that the clinical intervention may work under routine conditions. These results are promising but need to be verified in larger randomized studies. In addition, differences between the intervention centers emphasize the need to explore the mechanisms of impact.</p> Trial registration <p>This study was registered at ClinicalTrials.gov on 4 March 2021 (ref: NCT04799860).</p>