This research focuses on the synthesis, and application of cashew nut shell liquid (CNSL) derivatives—specifically urethane and borate-modified compounds—for the formulation of sustainable surface coatings using (CNSL + Propanol) as solvent. CNSL, a renewable, phenolic-rich resource, was chemically modified via urethanation and boration to enhance its performance characteristics for eco-friendly oil-based paints. Fourier Transform Infrared Spectroscopy (FTIR) confirmed successful derivatization, revealing characteristic functional groups such as –NHCOO– (urethane linkage) and B–O stretching vibrations, indicative of borate incorporation. Physicochemical analysis showed that the urethane derivative had lower density (0.96 g/ml), viscosity (2.6 Pa.s), and a refractive index of 1.48, along with a shorter drying time of 240 hours, making it suitable for rapid-curing coatings with minimal environmental impact. Conversely, the borate derivative exhibited higher density (1.3 g/ml), viscosity (3.2 Pa.s), and refractive index (1.67), with a prolonged drying time exceeding 528 hours, suggesting its potential for high-gloss, UV-resistant finishes. The study demonstrates that chemical modification of CNSL enhances its application potential in sustainable coatings, with urethane-CNSL derivatives being more suitable for fast-drying, user-friendly formulations, and borate derivatives offering functional advantages where long-term durability is essential. This work contributes to the development of bio-based alternatives in the coatings industry, aligning with green chemistry and circular economy goals.