BackgroundThere is moderate to strong evidence of the effectiveness of health-promotion interventions, but implementation in routine primary health care (PHC) has been slow. In the Act in Time project implementation support is provided for a health promotion practice using individually targeted lifestyle interventions in a PHC setting. Identifying health care professionals’ (HCPs’) perceptions of barriers and facilitators helps adapt implementation activities and achieve a more successful implementation. This study aimed, at a pre-implementation stage, to describe the expectations of managers, appointed internal facilitators (IFs) and HCPs on implementing a healthy lifestyle-promoting practice in PHC.MethodsIn this qualitative study five focus group discussions with 27 HCPs and 16 individual interviews with managers and appointed IFs were conducted at five PHC centres in central Sweden. The PHC centres are participating in the Act in Time project, evaluating the process and outcomes of a multifaceted implementation strategy for a healthy lifestyle-promoting practice. A deductive qualitative content analysis based on the Consolidated Framework for Implementation Research (CFIR) was followed using inductive analysis.ResultsTwelve constructs from four of five CFIR domains were derived: Innovation characteristics, Outer setting, Inner setting, and Characteristics of individuals. These domains are related to the expectations of HCPs to implement a healthy lifestyle-promoting practice, which includes facilitating factors and barriers. The inductive analysis showed that the HCPs perceived a need for a health-promotion approach to PHC. It serves the needs of the patients and the expectations of the HCPs, but lifestyle interventions must be co-produced with the patient. The HCPs expected that changing routine practice into a healthy lifestyle-promoting practice would be challenging, requiring sustainability, improved structures, cooperation in inter-professional teams, and a common purpose. A collective understanding of the purpose of changing practice was vital to successful implementation.ConclusionsThe HCPs valued implementing a healthy lifestyle-promoting practice in a PHC setting. However, changing routine methods was challenging, implying that the implementation strategy should address obstacles and facilitating factors identified by the HCPs.Trial registrationThis study is part of the Act in Time project, registered in ClinicalTrials.gov with the numberNCT04799860. Registered 03 March 2021.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12875-023-02079-5.