The aim of the study was to investigate the use of direct heterogeneous esterification method of extracted fibers from Leptadenia pyrotechnica khimp (Leptadenia pyrotechnica) and date palm tree (Phoenix dactylifera L.) using adipic and citric acids. Homogeneous esterification leads to the degradation of lignocellulosic material, making it impossible to obtain a pure ester of extracted crude fiber by this method. Methods. The esterification reaction was carried out from three samples of the plant Leptadenia pyrotechnica, Phoenix dactylifera L. leaf, and fiber) were extracted as crude fibers and used in the heterogeneous esterification process. The total esterified fibers were six esters (each sample esterified with citric and adipic acid). The study employed ordinary laboratory equipment together with Fourier Transformation Infrared (FTIR) spectroscopy. The results showed that the ester contents were in the range 21.6% to 28%. The degree of substitutions was in the range 0.38 to 0.57. Conclusion. This process was simple and effective in producing esterified extracted plants fibers with a desirable degree of substitution.