Obesity is an ingrained health problem with а multifactorial origin and а long history, thereby innovations in the treatment strategies are of great importance. In the search of a remedy for excessive weight gain, we have directed our investigations to phytochemicals as valuable bioactive compounds. Betulinic acid (BA), among the other triterpenoids, is known for its anti-inflammatory and anti-neoplastic properties. In addition, a previous study of ours has demonstrated а potent anti-adipogenic effect of BA in human adipocytes. Therefore, we aimed here to further verify the anti-obesogenic effect of BA in vivo in Caenorhabditis elegans. Induction of lipid accumulation in the nematodes was modelled with glucose-supplemented media, followed by treatment with BA (10–50 μM) or orlistat (12 μM) as a control anti-obesity medication. Oil red O and Nile red staining were applied to provide quantification of accumulated lipids. Analysis of the relative expression of genes, related to lipid metabolism suggested molecular mechanism of lipid-reducing action of BA in C. elegans. Treatment of nematodes with BA significantly decreased the lipid accumulation, downregulated desaturases involved in lipogenesis (fat-5, fat-6 and fat-7), modulated key transcription factors (nhr-49 and hlh-11) and microRNAs (miR-60, lin-4, let-7 and miR-786) associated with the lipid metabolism. Collectively, the current research provides additional insight on the molecular mechanism of the BA’s anti-obesogenic effect in vivo. Furthermore, it validates the potential of BA as a candidate compound in obesity management by reducing lipid accumulation.