Contact angle and surface tension measurements reveal wetting characteristics of materials, which are very essential for both fundamental research and manufacturing processes. Among many types of techniques, optical contact angle measurement is considered to be the most convenient method and has been widely used. This scientific operating procedure (SOP) provides general guidance for using an optical contact angle measurement system (e.g., an AST VCA Optima system), for determining contact angle and surface tension of nanomaterials in solution. Procedures and recommendations for sample preparation, instrument preparation, sample analysis, and results analysis are included. This procedure was tested on a variety of nanomaterial dispersions.