Lymphatic filariasis, caused by Brugia malayi, leads to chronic lymphatic dysfunction and lymphedema. The molecular mechanisms underlying interactions between filarial worms and their hosts remain poorly understood. Using untargeted metabolomics, we identify previously unknown acetylcholine analogs synthesized from leucine and isoleucine that are secreted by Brugia adult males. In the mammalian host, these metabolites selectively activate host M2 muscarinic acetylcholine receptors, alter lymphatic endothelial cell integrity, and trigger constriction of lymphatic vessels. These metabolites added to cultures also reduce microfilarial production in B. malayi and egg-laying in Caenorhabditis elegans, implying a role in regulating nematode reproduction. Their production is potently inhibited by ethacrynic acid, an existing FDA-approved drug. Our findings reveal a previously unexplored role for filarial-derived cholinergic signaling in parasite reproduction that impacts host lymphatic homeostasis. This work offers insights into the biochemical adaptations that function in the worm life cycle and reveals potential metabolic vulnerabilities in filarial worms.