In this study, copper and brass plates of 3-mm thickness were joined by friction stir welding at three different rotation rates and traverse speeds. The goal of this study is to determine weldability and mechanical properties of welded copper and brass plates. In order to determine the mechanical and microstructure properties of these plates, microhardness, tensile, bending, optical microscope, scanning electron microscope, and X-ray diffraction examinations were made. The following results were obtained; due to dynamic recrystallization effect, the grains in the stirred zone became fine. Microhardness values of the stirred zone were observed between 87 and 255 HV. According to the X-ray diffraction results, no phase transformation was observed in the stirred zone. In the stirred zone, a small tunnel-shaped joint defect was observed. It was determined that when heat input decreased, the mechanical properties and microstrain increased.