The effects of land-use and climate change on the hydrologic regime of the Namnam Stream in the Koycegiz Watershed, Turkey, are quantified using a hydrologic simulation modeling system under a number of real and potential scenarios. The study shows that urbanization has induced severe modification in the magnitude, frequency, and duration of extreme flow conditions. The mean annual flows increased by 5% to 60% due to 0.1% to 50% increase in impervious surfaces. Additionally, confounding climate change impacts include an increase in low flow pulses of 2% when considering a decrease in precipitation by 20% and a decrease in low flow pulses of 12% when considering a 20% increase in precipitation. The watershed system under investigation is significantly more sensitive to climate change scenarios involving additional inputs of precipitation compared to scenarios involving reductions in precipitation and that these changes are compounded in the presence of major land-use change. These results suggest the need for erosion control, nutrient management and habitat conservation in light of rapid urbanization, as often typified in developing countries, and potential climate change to conserve essential watershed functions.