In animal models of inflammatory colitis, pathology can be ameliorated by several intestinal helminth parasites, including the mouse nematode Heligmosomoides polygyrus. To identify parasite products that may exert anti-inflammatory effects in vivo, we tested H. polygyrus excretory-secretory (HES) products, as well as a recombinantly-expressed parasite protein, TGM, that functionally mimics the mammalian immunomodulatory cytokine TGF-β. HES and TGM showed a degree of protection in DSS-induced colitis, with a reduction in inflammatory cytokines, but did not fully block the development of pathology. HES also showed little benefit in a similar acute TNBS-induced model. However, in a T cell transfer-mediated model with RAG-deficient mice, HES reduced disease scores if administered throughout the first 2 or 4 weeks following transfer but was less effective if treatment was delayed until 14 days after T cell transfer. Recombinant TGM similarly dampened colitis in RAG-deficient recipients of effector T cells, and was effective even if introduced only once symptoms had begun to be manifest. These results are a promising indication that TGM may replicate, and even surpass, the modulatory properties of native parasite HES.