Porous polyamide functionalized by plasma or various coatings has been investigated for oil/water separation. In literature, polyamide has rarely been studied for oil removal, and this work investigated the performance of bare polyamide 6.6 (nylon 6.6) in terms of the oil/water separation efficiency and the intrusion pressure, inspiring cost-effective solutions for large-scale oil removal in the industry. Both polyamide meshes possessing two-dimensional (2D) one-layer pores and nonwoven fabrics with three-dimensional (3D) irregular pores were found to be able to separate oil/water with a high efficiency above 98.5%. This finding was attributed to the dual underwater oleophobicity and underoil hydrophobicity of these polyamide samples. The roles of 2D and 3D structures in oil/water separation were illustrated, to provide a new insight into filter designing. Due to its greater intrusion pressure, the 3D netting structure was suggested as being more beneficial for oil/water separation than the 2D structure.