Wettability is a widely used property in many industrial applications. This study aimed at determining the wettability of long-chain paraffin surfaces by nonionic surfactants, nonylphenol polyethoxylates with different ethoxylation degrees. Interactions between solid and liquid phases were determined by appar ent contact angle measurements. The morphology was obtained by atomic force microscopy. The results demonstrated that the molar mass of paraffin has a direct influence on the wettability of the surfaces by surfactant solutions. The rise in paraffin molar mass promoted a reduction of the contact angle between solid–liquid interfaces due to the formation of surfaces with less roughness. An increase in the ethoxy lation degree of surfactants reduced the wettability, showing a tendency toward water behavior. It was observed thatthe melted paraffin crystallized more abruptly due to having a higher melting temperature, which impedes crystal formation and, consequently, decreases its roughnessWettability is a widely used property in many industrial applications. This study aimed at determining the wettability of long-chain paraffin surfaces by nonionic surfactants, nonylphenol polyethoxylates with different ethoxylation degrees. Interactions between solid and liquid phases were determined by appar ent contact angle measurements. The morphology was obtained by atomic force microscopy. The results demonstrated that the molar mass of paraffin has a direct influence on the wettability of the surfaces by surfactant solutions. The rise in paraffin molar mass promoted a reduction of the contact angle between solid–liquid interfaces due to the formation of surfaces with less roughness. An increase in the ethoxy lation degree of surfactants reduced the wettability, showing a tendency toward water behavior. It was observed thatthe melted paraffin crystallized more abruptly due to having a higher melting temperature, which impedes crystal formation and, consequently, decreases its roughness