In order to study the nature, type, and magnitude of interactions in the binary mixtures of pentanoic acid and a series of 1-alkanol from 1-pentanol up to 1-decanol, Kirkwood integrals along with the experimental methods have been used and reported at T = 298.15 K. Negative values of V-m(E), G(ii), G(ij), Delta n(ii), Delta n(ij), and delta(ii) and positive values of G(ij), Delta n(ij), and delta(ij) indicate the fact that in the mixtures the tendency of the unlike molecular components to form the new interactions and stay together is much higher than the pure state. Investigating the changes in the calculated quantities for different mixtures shows that with the increase in the length of the alcoholic chain the tendency of the heterogeneous molecules to interact with each other decreases. Variations in the V-m(E) values are in the same direction as the Kirkwood integrals, and mentioned data for binary systems are reported for the first time.