We reported two patients of cardioembolic stroke with stepwise progression. Magnetic resonance angiography (MRA) or computed tomographic angiography (CTA) showed narrowing of the middle cerebral artery (MCA) in both patients at the acute phase of onset. Case 1 was classified as "undetermined" based on the TOAST classification although his electrocardiogram revealed atrial fibrillation. Case 2 was classified as "large artery atherosclerosis" with no evidence of cardioembolic source at the acute phase of onset. Follow-up MRA was performed at seventeen days after the onset in case 1 and ten days after the onset in case 2 respectively, which showed complete recanalization of the MCA in each case. The presence of cardioembolic source was also detected in both patients at that time, resulting in the final diagnosis of cardioembolic stroke. Cardioembolic stroke may occasionally present in a stepwise manner suggesting a thrombotic process. When MRA shows stenosis or occlusion of the arteries supplying the cortical areas at the acute phase of onset, it is advisable to examine recanalization of these arteries by follow-up MRA with simultaneous efforts to find out the possible embolic source.