<p>The expanding diversity of biofuels necessitates the development of thermodynamic models, as accurate property prediction is essential for efficient utilization, robust process design, and reduced reliance on fossil fuels. The speed of sound is a key thermodynamic property that enables the determination of many other properties. In this work, an accurate and globally applicable model was developed to predict the speed of sound in biodiesels and their primary pure components—fatty acid methyl esters (FAMEs) and fatty acid ethyl esters (FAEEs)—at atmospheric pressure, and subsequently extended to high-pressure conditions. A total of 3069 experimental speed of sound data points were compiled for 22 fatty acid alkyl esters over a temperature range of 278.15–608.15 K and pressures up to 210 MPa. The results show that the model yields average absolute relative deviations (AARD%) of just 0.41% at atmospheric pressure and 1.03% under high-pressure conditions. Also, the proposed correlation, combined with the ideal mixture rule, was applied to predict the speed of sound in 18 biodiesel fuels, achieving an overall deviation of only 0.31%. Accordingly, the proposed model can reliably predict the speed of sound in the studied compounds across a wide range of thermodynamic conditions.</p>