Mutations in the gene encoding the peroxisomal ATP-binding cassette transporter (ABCD1) cause elevations in very long-chain fatty acids (VLCFAs) and the neurodegenerative disease adrenoleukodystrophy (ALD). In most adults, this manifests as the spinal cord axonopathy adrenomyeloneuropathy (AMN). A challenge in virus-based gene therapy in AMN is how to achieve functional gene correction to the entire spinal cord while minimizing leakage into the systemic circulation, which could contribute to toxicity. In the present study, we used an osmotic pump to deliver adeno-associated viral (AAV) vector into the lumbar cerebrospinal fluid space in mice. We report that slow intrathecal delivery of recombinant AAV serotype 9 (rAAV9) achieves efficient gene transfer across the spinal cord and dorsal root ganglia as demonstrated with two different transgenes, GFP and ABCD1. In the Abcd1-/- mouse, gene correction after continuous rAAV9-CBA-hABCD1 delivery led to a 20% decrease in VLCFA levels in spinal cord compared with controls. The major cell types transduced were astrocytes, vascular endothelial cells, and neurons. Importantly, rAAV9 delivered intrathecally by osmotic pump, in contrast to bolus injection, reduced systemic leakage into peripheral organs, particularly liver and heart tissue.