Coronary angioscopy is a useful tool for understanding plaque characteristics through the plaque color and surface thrombus formation. We experienced an interesting case of a newly developed yellow neointima 400 days after a sirolimus-eluting stent implantation. A 72-year-old woman suffering from angina pectoris was admitted to our hospital. Coronary angiography revealed severe stenosis at the proximal left descending artery and she was implanted with a sirolimus-eluting stent. Coronary angioscopic observation immediately after stent implantation revealed the presence of yellow plaque only at the most severe stenosis lesion in the stent placement site. We performed a coronary angiography 400 days after the sirolimus-eluting stent implantation and did not find an in-stent restenosis. An intravascular ultrasound indicated minimum neointimal formation. By coronary angioscopy, we could clearly observe that the neointima had covered the surface of the stent struts; the stent struts were barely visible under the neointima. Surprisingly, neointima formed in response to the sirolimus-eluting stent was entirely yellow. Precise mechanisms of producing yellow neointima was unknown, we may observe a pathologic neointima induced by sirolimus-eluting stent.