Currently, no curative treatment is available for spinal muscular atrophy (SMA). Since the degeneration of spinal motor neurons in SMA is mediated by apoptosis, over-expression of an anti-apoptotic factor, Bcl-x(L), may benefit SMA. Here, we crossed a mouse model of SMA with Bcl-x(L) transgenic mice to create SMA/Bcl-x(L) mice. The Bcl-x(L) expression in the spinal neurons of SMA/Bcl-x(L) mice was nearly double that in SMA mice. SMA/Bcl-x(L) mice showed preserved motor function, normalized electrophysiological tests, diminished muscle atrophy, and less motor neuron degeneration. In addition, the life span of SMA/Bcl-x(L) mice was 1.5 times longer than that of SMA mice. Therefore, over-expression of Bcl-x(L) has a potential for amelioration of SMA, and Bcl-x(L) may be another attractive therapeutic target other than survival motor neuron (SMN) protein for use in future drug screening for SMA.