Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is a polyglutamine disorder caused by an abnormal trinucleotide (CAG) expansion in the ATXN3 gene, leading to neurodegeneration. This translates into severe impairments across the patient’s body functions, and there are no therapies to halt or slow disease progression. Thus, there is an urgent need to identify novel molecular targets to develop disease-modifying therapies. Previously, it was shown that the loss of the tRNA methyltransferase 2 homolog A (TRMT2A) reduced polyglutamine toxicity and aggregation in SCA3/MJD fibroblasts and Drosophila models. Despite this, the therapeutic impact of Trmt2a knockout in a SCA3/MJD mammal model was not unaddressed. The present work aims to analyze in detail the impact of a Trmt2a knockout in a transgenic SCA3/MJD mouse model. Briefly, SCA3/MJD mice with the genotypes Trmt2a+/+, Trmt2a+/- and Trmt2a-/- (full knockout) underwent motor behavioral tests every 4 weeks for 12 weeks, including rotarod, footprint, grip strength, and swimming tests. Our findings show that the response of mice motor’s function is dependent on the dosage of TRMT2A protein. Compared to the control groups, SCA3/MJD Trmt2a-/- mice exhibited slower motor deterioration and better gait performance. This is concomitant with an increase in the number of Purkinje cells, suggesting neuroprotection. Furthermore, pathological aggregates diminished in the retina in the absence of TRMT2A. These findings suggest that TRMT2A holds promise as a potent therapeutic target, potentially paving the way for novel disease-modifying treatments for SCA3/MJD.