Background <p>As a well-established clinical model, ambulatory surgery has been routinely performed in thoracic surgery. Accordingly, this study aimed to investigate home-based physical activity, functional capacity, mental health in patients undergoing ambulatory VATS for lung cancer.</p> Method <p>This study prospectively observed the changes in physical activity, functional capacity, mental health and quality of life on 1 month after surgery, with a comparison between the postoperative and preoperative to identify the indicators associated with early postoperative mobility, and further screened out the potential preoperative predictors for postoperative mobility. Among 150 patients assessed for eligibility, 97 were enrolled, 82 underwent day-case VATS wedge resection, and 72 had complete 4-week follow-up data and constituted the complete-case analytic cohort.</p> Result <p>A total of 72 patients underwent day-case VATS, were discharged within 23&#xa0;h postoperatively, and completed the 4-week follow-up. The cohort had a mean age of 50.4 ± 12.0 years, with 88.9% stageⅠA1 and 11.1% stageⅠA2 lung cancer. The compliance of wearing Actigraph accelerometers was satisfactory within 4 weeks after surgery. During the 4-week follow-up, patients showed a significant upward trend in daily step count, mean daily METs, and moderate-intensity physical activity time (all <i>P</i> &lt; 0.05), while light-intensity activity decreased notably from week 1 to week 2 and remained stable thereafter. No significant changes were observed in sedentary time across the 4 weeks. Compared with the preoperative baseline, significant decreases were observed in 6MWD(<i>P</i> = 0.043), MEP(<i>P</i> = 0.001), mMRC grade(<i>P</i> = 0.044) and EQ-VAS score(<i>P</i> = 0.002), whereas SF-12 score(<i>P</i> = 0.003) increased significantly. Correlation analysis showed week 1 step count correlated significantly with preservation of exercise capacity (Δ6MWT) (<i>r</i> = 0.369, <i>P</i> = 0.035). Univariate linear regression identified higher GAD-7 scores were strongly associated with lower activity levels (<i>P</i> = 0.02). Safety outcomes were analyzed in the all-operated cohort (<i>n</i> = 82, primary safety population) and the pathology-confirmed malignant cohort (<i>n</i> = 78, secondary safety population). Two patients (2.44%, 95% CI 0.30–8.53%) experienced postoperative complications requiring 30-day readmission- for pulmonary infection. No 30-day reoperation or mortality was observed (0/82, 95% CI 0–4.40%).</p> Conclusion <p>Patients undergoing day-case VATS wedge resection showed a weekly increase in home-based activity, reaching near physical activity levels of normal healthy individuals by week 4 without full recovery of preoperative physical capacity. The mean daily step count at week 1 was correlated with functional performance at week 4. Preoperative anxiety level was inversely associated with physical activity within the first postoperative week, indicating that higher preoperative anxiety corresponded to lower postoperative physical activity level.</p>