The cement has to be ground fine enough and have the optimum particle size distribution (PSD) to meet the requirements such as strength properties and setting times in current standards. As it takes quite a long time to determine especially the late strength, grinding has to be based on the cement fineness and the PSD. In this study, the effects of fatty acids were investigated on the PSD of Portland cement. Experimental results showed that the fineness of the cement was decreased for that replaced with 0.025 wt.% lauric acid (LA), myristic acid (MA) and sunflower oil acid (SO), then increased for the other additions. The fineness measurements revealed that the cement grains aggregated for an amount of 0.025 % (w) during the grinding. Also, when the PSD of the ground cement is examined, the relationship between the saturated and the unsaturated components is evident that milling the cement clinker together with 0.1% (w) LA and 0.1 wt. % MA gave the finer cement from that with 0.1 wt.% SO.