After the declaration of the coronavirus-2019 (COVID-19) pandemic and the detection of the CO VID-19 case in Turkey, a series of non-pharmaceutical measures were implemented to reduce the numberof contacts at the national level. The aim of this study was to determine the change in the epidemicreproduction rate ($R_0$) with non-pharmaceutical interventions including curfews starting with the firstreported case in Istanbul and to evaluate the effectiveness of interventions by estimating the numberof cases and deaths using a dynamic compartmental model. While keeping transmission probability(beta) as 3% and incubation period as seven days, we developed five scenarios that represented non pharmaceutical interventions The first scenario was “if nothing was done” and the last scenario was “cur few”. The contact matrix of 16 age-groups created by Prem et al. was used in the study as the contactmatrix of “if nothing was done” as scenario 1. For all other scenarios (2-5) contact matrices assumptionswere created and $R_0$ values were calculated for the whole of Istanbul according to age groups for all fivescenarios. For each scenario, “the number of cases and COVID-related deaths” for one year from the daythe first case was detected were calculated with the mathematical modeling method. In the absence ofany intervention, $R_0$ value was estimated as 2.86 in Istanbul. Among age-groups, the largest $R_0$ value wasobserved in ages 15-19, 10-14, 5-9, 20-24 and the values were 5.22, 4.37, 3.32, and 3.33; respectively.Due to school closings and flexible work hours, $R_0$ values decreased to 2.02, 1.84, 1.63 and 1.85 in thesame age-groups. With the addition of a curfew for the population under the age of 20 to the abovemeasures, the $R_0$ values for all age groups were reduced to less than one. When $R_0$ values for Istanbul was2.86 and 1.55 based on our model results, the number of cases and deaths per year were determined asapproximately 14 million and 2 million and 2.5 million and 327.000, respectively. School closures weredetermined as the most effective non-pharmaceutical intervention. Non-pharmaceutical measures withthe addition of curfews under the age of 20 and over the age of 65 to the school closings and flexibleworking hours were identified as effective methods in controlling the COVID-19 epidemic in Istanbul.While the results of this study may not reflect real life data, it has the potential of helping public healthpolicy makers to decide on which non-pharmaceutical interventions are the most effective.