In plants, the primary form of energy stored form in seed lipid droplets, triacylglycerol (TAG), is catabolized during germination to support pre-photosynthetic growth. While this process is essential for seedling development, it is incompletely understood. In a screen for Arabidopsis thaliana mutants with delayed lipid droplet coat protein degradation, five independent mutations in PECTIN METHYLESTERASE31 (PME31) were recovered. In addition to delayed coat protein degradation, pme31 mutant seedlings exhibited sustained lipid droplets and elevated levels of several TAG and diacylglycerol species. Although structural prediction classified PME31 as a pectinesterase, it also resembled the putative E.coli lipase, YbhC. A fluorescent PME31 reporter was cytosolic and associated with peroxisomes, the site of fatty acid catabolism, during lipid mobilization. These findings suggest that, in contrast to most PMEs, which modify cell wall pectin, PME31 functions in lipid mobilization at the peroxisome.