Trabzon Province with a total population of 757,898 is the biggest city on the Southeastern Black Sea Coast. Domestic water demand of the city is supplied by the Degirmendere and Galyan streams after treatment at the drinking water treatment plants of the Trabzon Metropolitan Municipality. The main purpose of this study is to monitor and assess drinking water quality of these surface water resources before treatment with reference to 30 water-quality indicators. The monitoring results covering 1-year period revealed that each stream had high-quality water except for total Kjeldahl nitrogen, orthophosphate phosphorus, and total iron, by which each stream was classified as slightly polluted according to the Turkish Surface Water Quality Regulation. The results for the untreated stream waters were well below the permissible levels mandated or proposed by national and international references except for total iron. However, the post-treatment quality and safety of the stream waters used for drinking purposes matched the standards as indicated in the drinking water-quality reports of the Trabzon Metropolitan Municipality.