In our study, we have aimed first to isolate an a-L-arabinofuranosidase (ALAF) enzyme, 58.0 kDa, from a thermophilic organism; Thermophilic Geobacillus sp. by using molecular cloning techniques, then to characterize this enzyme via biochemical methods. Throughout the characterization studies, we have investigated the optimum conditions for the highest enzyme activity by means of pH and temperature by using pNP--L-arabinofuranoside as substrate. Also, effect of various metal ions, some specific chemicals and common organic solvents on enzyme activity was studied. Due to the fact that -L-arabinofuranosidases mainly hydrolyze -L-arabinofuranosyl residues of L-arabinose containing polysaccharides, enzyme activity towards sugar beet arabinan was also studied. Our enzyme exhibited activity in a broad pH range between pH 3.0-10.0 at 50°C and between 30-90°C in Na-acetate buffer pH 5.0. Optimum activity towards pNP--L-arabinofuranoside was obtained at pH 5.0 and at 70°C. Kinetic studies showed that our enzyme has a Km value as 0.19 mM and Vmax as 18.6 Abs/min/ml towards pNP--L-arabinofuranoside and Km value as 0.1 mM and Vmax as 8.1 Abs/min/ml towards sugar beet arabinan.