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Objective: Coronavirus disease-2019 (COVID-19), which caused a big outbreak, was first detected in Wuhan, China on 31st of December, 2019, and began to spread all over the world rapidly. The first case in Turkey was detected on the 11th of March, 2020. This study aims to calculate time-dependent (TD) reproduction number (Rt) using three different serial interval values in the late phase of the COVID-19 pandemic for Turkey. Material and Methods: TD model was used for estimation of reproduction number. For the serial interval of the coronavirus, the serial interval values of 4±2.5 and 6±3 days were used together with the severe acute respiratory syndrome and Middle East respiratory syndrome serial interval mean of 8±3.6. Gamma distribution was used for serial interval estimates. The bootstrap method with 1,000 simulations was used for all reproduction number confidence interval estimates. Results: Using 8±3.6, 6±3 and 4±2.5 serial interval values, the mean reproduction number (Rt) calculated for Turkey with the TD model was 2.06 (1.92-2.21), 1.70 (1.58-1.81), and 1.39 (1.30- 1.48), respectively. The confidence intervals of the reproduction number values calculated for Turkey range from 1.30 (lowest) to 2.21 (highest). Conclusion: According to the TD model results, from the first day when the pandemic started in Turkey to the 32nd (11th of April 2020) and 33rd (12th of April 2020) days, the Rt value decreased below 1 and the outbreak started to demonstrate a breaking point. Lower Rt in Turkey compared to the other epicenters of the world may indicate that Turkey was quicker in implementing preventive measures much earlier than the other countries. [ABSTRACT FROM AUTHOR]