(1) Background: The COVID-19 pandemic has introduced a major disruption to the delivery of secondary prevention measures in patients with established atherosclerotic cardiovascular disease (CVD). It required a rapid and widespread adoption of new medical services, including the use of telemedicine. This study aimed to examine the impact of COVID-19 on secondary prevention in patients with coronary artery bypass grafting (CABG) and to evaluate the effectiveness of the telemedicine application for the implementation of lifestyle change measures, remote monitoring, and treatment regimen adjustment; (2) Methods: This prospective study on 194 CABG patients evaluated three consecutive years between 2019 and 2022 in the pre-pandemic period by face-to-face visits and during the pandemic by teleconsultations or hybrid follow-up. Variables of interest were compared between four periods: pre-pandemic-pre-P (1 March 2019-29 February 2020), lockdown-Lock (1 March-31 August 2020), restrictive-pandemic-Restr-P (1 September 2020-28 February 2021), and relaxed-pandemic-Rel-P (1 March 2021-1 March 2022). (3) Results: The average values of the lipidogram, blood sugar, and uric acid increased during Lock and Restr-P, but, through the use of teleprevention, they returned to the pre-pandemic level or even below this level. The exception was blood sugar, which remained high in Rel-P. The number of newly diagnosed patients with diabetes also increased, with most of them having moderate forms of COVID. During Lock and Res-P, the percentage of obese, smoking, or hypertensive patients increased, but, through the use of teleprevention, we managed to reduce it, although it remained slightly higher than the pre-pandemic level. Physical activity decreased in the first year of the pandemic, but, in Rel-P, CABG patients became more active than before the pandemic (4) Conclusions: The use of telemedicine for cardiovascular secondary prevention allowed us to not only continue seeing CABG patients but, also, to adjust their medication and to expand cardiovascular preventive counseling and testing with favorable results, especially during the second year of the pandemic.