For the flotation of complex Cu-Zn sulphide ores; mineralogical texture of ore, liberation particle size of minerals, selection of suitable flotation reagents and the technological properties of flotation machines are very important. The ore to be investigated in this study is complex Cu-Zn sulphide ore taken from East Karadeniz region that have some problems depending on fine liberation particle size. Ore grade is 2.75% Cu and 6.75% Zn. In this study, the determination of particle liberation size and the effect of grinding time on grade and recovery of complex Cu-Zn sulphide ore were investigated by flotation method. The Jameson flotation cell is a type of flotation device that has a high flotation performance and used for fine grained minerals having problematic flotation behavior. The Jameson cell already were used for concentration of various metallic ores in pilot and full scale, successfully and have much instrumental parameters that affect the flotation recovery, such as down comer diameter, plunging length of down comer, etc. Chalcopyrite liberation size was determined as -38+25 mm by mineralogical analyses. To reach this liberation size and to find out the optimum grinding time, the samples were ground at different grinding times, and then these samples were floated in Jameson cell. Afterwards, the concentrate grades and flotation recoveries for each different grind out sample were determined. It was observed that the optimum liberation size obtained from mineralogical analyses was consistent with the flotation test results.