BACKGROUND: Studies report that increased levels of patient activation is associated with increased engagement with the health care system, better adherence to treatment protocols, and improved health outcomes. This study aims to evaluate the outcomes of a 12-month Patient-Centred Medical Home (PCMH) model called 'WellNet' on the activation levels of patients with one or more chronic diseases in general practices across Northern Sydney, Australia. METHODS: A total of 636 patients aged 40 years and above with one or more chronic conditions consented to participate in the WellNet program which was delivered across six general practices in Northern Sydney, Australia. The WellNet intervention includes team-based care with general physicians and trained chronic disease management care coordinators collaborating with patients in designing a patient-tailored care plan with improved self-management support and care navigation according to the level of risk and health care needs. The level of patient activation was measured using the validated PAM 13-item scale at baseline and follow-up. A before and after case-series design was employed to determine the adjusted mean differences between baseline and 12-months using repeated measures analysis of covariance (ANCOVA). Additionally, the backward stepwise multivariable regression models were employed to identify significant predictors of activation at follow-up. RESULTS: Of the 626 patients, 420 reported their PAM scores at follow-up. The mean (SD) baseline PAM score was 57.9 (13.0). The adjusted model showed significant mean difference in PAM scores by increase of 6.5 (95% CI 5.0-8.1; p-value< 0.001) after controlling for baseline covariates. The multivariable regression models showed that older age (B = - 0.14; 95% CI -0.28, - 0.01) and private insurance (uninsured patients) (B = - 3.41; 95% CI -6.50, - 0.32) were significantly associated with lower PAM scores at 12 months whereas higher baseline PAM score (B = 0.48; 95% CI 0.37, 0.59) was significantly associated with higher follow-up PAM score. CONCLUSION: The WellNet study is the first of its kind in Australia to report on changes in the patient activation levels among patients with one or more chronic diseases. PCMH has the potential to improve patient activation and engagement which can lead to long-term health benefits and sustained self-management behaviours.