We herein report the case of a 44-year-old woman who developed protein-losing gastroenteropathy (PLGE) with hypoalbuminemia as the first manifestation of mixed connective tissue disease (MCTD). Albumin leakage from the stomach and intestinal tract was demonstrated by 99mTc-labeled human serum albumin scintigraphy. The patient's response to prednisolone therapy was insufficient; therefore, additional cyclosporin A (CsA) treatment was administered, and clinical remission was achieved. We concluded that although PLGE is a rare complication of MCTD, it may manifest as an initial clinical episode of MCTD. Furthermore, CsA can be a useful treatment option for refractory PLGE related to MCTD.