The effects of carboxylic acid type surfactants with different hydrocarbon chain lengths and molecular structures such as benzoic acid, oleic acid, acrylic acid and stearic acid on the surface modification of marble waste powder (MWP) have been investigated. For this purpose, composites have been produced in different compositions by using unmodified MWP and 5 to 10 wt% modified (surface coated) MWP containing silicons and then the hydrophobicity grades of the surfaces of these composites have been evaluated by determining the changes in the water-contact angle values. The results obtained show that the most suitable surfactant is steric acid to produce MWP powders having hydrophobic surfaces.