Background: Sustainability of adherence to clinical practice guidelines (CPGs) represents an important indicator of the successful implementation in the primary care setting. Aim: To explore the sustainability of primary care providers’ adherence to CPGs after receiving planned guideline implementation strategies, activities, or programmes. Methods: Cochrane Central Register of Controlled Trials (CENTRAL); Cumulative Index to Nursing and Allied Health Literature (CINAHL); EMBase; Joanna Briggs Institute; Journals@Ovid; Medline; PsycoINFO; PubMed, and Web of Science were searched from January 2000 through May 2021 to identify relevant studies. Studies evaluating the sustainability of primary care providers’ (PCPs’) adherence to CPGs in primary care after any planned guideline implementation strategies, activities, or programmes were included. Two reviewers extracted data from the included studies and assessed methodological quality independently. Narrative synthesis of the findings was conducted. Results: Eleven studies were included. These studies evaluated the sustainability of adherence to CPGs related to drug prescribing, disease management, cancer screening, and hand hygiene in primary care. Educational outreach visits, teaching sessions, reminders, audit and feedback, and printed materials were utilized in the included studies as guideline implementation strategies. None of the included studies utilized purpose-designed measurements to evaluate the extent of sustainability. Three studies showed positive sustainability results, three studies showed mixed sustainability results, and four studies reported no significant changes in the sustainability of adherence to CPGs. Overall, it was difficult to quantify the extent to which CPG-based healthcare behaviours were fully sustained based on the variety of results reported in the included studies. Conclusion: Current guideline implementation strategies may potentially improve the sustainability of PCPs’ adherence to CPGs. However, the literature reveals a limited body of evidence for any given guideline implementation strategy. Further research, including the development of a validated purpose-designed sustainability tool, is required to address this important clinical issue. Trial registration: The study protocol has been registered at PROSPERO (No. CRD42021259748).