CLN1 disease is caused by mutations in the PPT1 gene, leading to lysosomal dysfunction and progressive motor and neurological declines. Currently, no effective therapy exists, prompting us to test N-acetyl-leucine (NALL), a drug approved for treating Niemann-Pick disease Type C (NPC). We evaluated the therapeutic potential of NALL in Ppt1⁻/⁻mice, delivering it in modified chow 0.1g/kg (or standard chow as a placebo control), starting either immediately post-weaning or delaying NALL administration to 4 months of age, representing disease midstage. We used previously defined gait and rotarod phenotypes, and brain pathology as outcome measures, in addition to assessing any impact upon survival. We first identified gait parameters sensitive to disease progression, finding 54 parameters as reliable indicators of motor decline in Ppt1⁻/⁻ mice and used these to evaluate NALL treatment response. Early NALL administration led to significant improvement in four of these gait parameters, related to variation in body speed, suggesting enhanced movement stability. However, coordination-related variables remained unaffected, and no extension of lifespan was observed with either early or delayed treatment. Analysis of brain pathology at disease end stage confirmed hallmark features of CLN1 pathology, including pronounced lysosomal storage material accumulation (SCMAS), and activation of microglia (CD68) and astrocytes (GFAP) in the cortex and thalamus. NALL treatment, regardless of when it was started, altered some of these pathological markers, but none significantly compared to placebo treated Ppt1⁻/⁻ mice. Taken together, these findings suggest that NALL has limited efficacy in CLN1 mice. When given early, it can moderately improve movement stability and reduce some signs of brain inflammation. However, it does not improve coordination, prevent brain damage, or extend lifespan. While NALL alone does not alter disease progression, it may still be useful as part of a combination therapy approach, and is the subject of future proposed studies.