TIE1 is a cell surface protein expressed in endothelial cells. Involved in angiogenesis and lymphangiogenesis, including morphogenesis of lymphatic valves, TIE1 is important for lymphatic system functional integrity. The main purpose of this study was to identify different variants in theTIE1gene that could be associated with lymphatic malformations or dysfunction and predisposition for lymphedema. In a cohort of 235 Italian lymphedema patients, who tested negative for variants in known lymphedema genes, we performed a further test for new candidate genes, includingTIE1. Three probands carried different variants inTIE1. Two of these segregated with lymphedema or lymphatic dysfunction in familial cases. Variants inTIE1could contribute to the onset of lymphedema. On the basis of our findings, we proposeTIE1as a candidate gene for comprehensive genetic testing of lymphedema.