Objective: To assess the proportion of participants reconsidering their willingness to undergo surgery after 3 and 12 months. Secondary aims were to analyze and compare the characteristics of individuals willing and unwilling to undergo joint surgery for osteoarthritis (OA) before a first-line intervention, and to study the association between pain intensity, walking difficulties, self-efficacy, and fear of movement with the willingness to undergo surgery. Methods: This was an observational study based on Swedish register data. We included 30,578 individuals with knee or hip OA who participated in a first-line intervention including education and exercise. Results: Individuals willing to undergo surgery at baseline showed a higher proportion of men (40% versus 27%) and more severe symptoms and disability. Respectively, 45% and 30% of the individuals with knee and hip OA who were willing to undergo surgery at baseline became unwilling after the intervention. At the end of the study period (12 months), 35% and 19% of those with knee and hip OA, respectively, who were willing to undergo surgery at baseline became unwilling. High pain intensity, walking difficulties, and fear of movement were associated with higher odds of being willing to undergo surgery at both follow-ups, while increased self-efficacy showed the opposite association. Conclusion: A first-line intervention for OA is associated with reduced willingness to undergo surgery, with a greater proportion among patients with knee OA than hip OA. Due to its temporal variability, willingness to undergo surgery should be used with care to deem surgery eligibility.