O-GlcNAcylation is an important post-translational modification of proteins and is known to regulate a number of pathways involved in cellular homeostasis. This involves dynamic and reversible modification of serine/threonine residues of different cellular proteins catalyzed by O-linked N-acetylglucosaminyltransferase (OGT) and O-linked N-acetylglucosaminidase (OGA) in antagonistic manner. We report here that decreasing O-GlcNAcylation enhances viability of neuronal cells expressing polyglutamine expanded huntingtin exon 1 protein fragment (mHtt). We further show that O-GlcNAcylation regulates the basal autophagic process and that suppression of O-GlcNAcylation significantly increases autophagic flux by enhancing the fusion of autophagosome with lysosome. This regulation considerably reduces toxic mHtt aggregates in eye imaginal discs, and partially restores rhabdomere morphology and vision in a fly model for Huntington's disease. The present study is significant in unravelling O-GlcNAcylation-dependent regulation of autophagic process in mediating mHtt toxicity. Therefore, targeting autophagic process through the suppression of O-GlcNAcylation may prove to be an important therapeutic target in Huntington disease.