Severe hypertriglyceridemia is a rare condition in pregnancy. We report a case of gestational, nonfamilial severe hypertriglyceridemia accompanied with gestational diabetes mellitus. Despite an intensive insulin regimen and dietary fat restriction plasma triglyceride levels were remained higher. After a plasmapheresis session, triglyceride levels were reduced nearly 40%. Since plasma glucose and triglyceride levels were higher, metformin therapy was administered. After two weeks of metformin therapy, plasma glucose levels were within target range and triglyceride level was reduced below 1000 mg/dl.