Noise pollution provoked by vehicles is a growing problem that negatively impacts health. For this reason, it is necessary to explore the possibility of improving sound insulation of some parts of the vehicle, such as commercial automotive paints or panels. This work deals with studying the incorporation of natural fibers into an acrylic commercial paint. Dispersions of microcrystalline cellulose (C) and nanocellulose (NC), extracted from commercial cellulose, type Iα, obtained by chemical methods (hydrogen peroxide and sodium hydroxide) and acid hydrolysis (sulfuric acid), were prepared at different concentrations (0.1, 1, 3, and 5 wt%). These formulations were applied onto 3003 aluminum substrates and characterized by Raman spectroscopy, X-ray diffraction (XRD), and optical microscopy. Moisture resistance and sound absorption capacity were also evaluated. Raman and XRD analyses confirmed the presence of cellulose and paint components such as titanium dioxide (TiO₂) in anatase and rutile phases. On the other hand, optical microscopy showed that NC presented better dispersion and less agglomerates than C. In acoustic performance, the results showed that the addition of C at 5 wt% led to the best noise attenuation compared to NC. C displayed values c.a. 2.4 dB (3.15%) in the minimum value and 1.7 dB (2.05%) in the maximum value compared to the paint. However, the incorporation of both materials increased moisture absorption. In conclusion, the addition of microcrystalline cellulose to automotive paints may be promising for automotive sound insulation.