Background: Cancer Care Ontario (CCO) implemented the Well Follow-up Care Initiative (WFCI) to transition low-risk breast cancer (BC) survivors from oncologist to primary care providers. The objective of this work was to compare both the health system resources utilized and their associated costs, among women in the WFCI (cases) and women who were not transitioned (controls). Methods: Cases were linked to provincial administrative databases and matched to a control group based on year of diagnosis, cancer stage, age, comorbidity, income, geographic area of residence, and prior health system use. Health system resource utilization (physician, hospitalization, diagnostics, medication, and homecare) was ascertained per group. The annual mean and median costs (CAD 2014) per patient were determined. Annualized incremental costs between cases and controls were estimated using generalized estimating equations, accounting for matched pairs. Results: Results are based on 2,324 cases and 2,324 controls (mean age 64.4 and 64.9 years, respectively). During an average of 2.5 years of follow-up since the transition date, there were significant differences between the two groups for mean annual visits per patient with a medical oncologist (0.4 vs. 1.3, p<0.001) and radiation oncologist (0.2 vs. 0.4, p<0.001). There was no significant difference in mean annual family physician visits per patient (7.4 vs. 7.9, p=0.082). The intervention group had fewer inpatient hospitalizations (75.6% vs. 79.9%) and cancer clinic visits (84.9% vs. 94.0%). While there was a higher number of mammograms for cases compared to controls, other diagnostic tests (bone scan, CT, MRI, ultrasound, and x-rays) were done less frequently. The model was associated with a 39.3% reduction in mean annual costs ($6,575 among cases and $10,832 among controls) and a 22.1% reduction in median annual costs ($2,261 among cases and $2,903 among controls). Conclusions: Transitioning BC survivors to primary care was associated with fewer health system resources and had a lower annual mean cost per patient than women who were not transitioned.