The global minimum structures of AlB3H2n (n=0-6) clusters are determined using the stochastic search method at the B3LYP/6-31G level of theory. These initially specified geometries are recalculated using B3LYP and CCSD(T) methods using the 6-311++G(**) basis set. The structural and electronic properties of the two lowest-lying isomers are presented. The structural parameters obtained for aluminum borohydride are compared with the experimental and theoretical results. The H-2 fragmentation energies of the most stable isomers are investigated. Chemical bonding analyses for the global minimum of AlB3H2n (n=0-6) clusters are performed using the adaptive natural density partitioning method.