PLA2G6-associated neurodegeneration (PLAN) is a group of rare genetic disorders characterised by progressive neurodegeneration resulting from mutations in the PLA2G6 gene, encoding a calcium-independent phospholipase enzyme. Here, we explored the effects of decanoic acid (DA), a medium-chain fatty acid, in fruit-fly Drosophila melanogaster models of PLAN and showed that DA treatment significantly extends the lifespan, reduces bang sensitivity, and improves resistance to heat shock stress. Transcriptional analysis showed that DA affects genes in key signalling pathways, including Insulin/Insulin-like Growth Factor, mTOR, heat shock response, Sirtuin, autophagy, and mitochondrial function. Additionally, DA treatment alters the metabolite profiles in PLAN model flies, with the most pronounced changes observed in gut tissue. Pathway analysis of these metabolomic shifts highlighted potential therapeutic effects of DA in several pathways, including ATP-binding cassette (ABC) transporters, purine metabolism, cAMP signalling, and neuroactive ligand-receptor interactions. These findings suggest that DA may be a promising therapeutic agent for PLAN, offering insights into the mechanisms of the disease and paving the way for future research on medium-chain fatty acids as potential treatments for neurodegenerative diseases.