Near-infrared spectroscopy (NIRS) has been utilized in the recent decades for monitoring stroke brain function by measuring the changes in the concentrations of oxygenated and deoxygenated hemoglobin. Although there is evidence that motor rehabilitation can enhance motor recovery in stroke survivors with motor deficits, the brain function and reorganization related to motor rehabilitation efficacy have not been well understood. Neuroimaging studies such as with functional magnetic resonance imaging (fMPI) have been limited to simple rehabilitation tasks on upper extremities because artifact from excessive motion may interfere with the images. The detection of brain activities under larger body motion such as gait or cycling has become possible with the development of the optical brain imaging technique of NIRS being utilized in the rehabilitation field. This article first introduces the general principles and technological development of NIRS. The applications of NIRS in rehabilitation tasks and effects are reviewed emphasizing the role NIRS has played in this field so far. A brief discussion of advantages and suggestions for NIRS in stroke rehabilitation follows. Although NIRS studies of stroke rehabilitation are still novel, this review and our preliminary studies indicate that brain imaging using NIRS has great potential to provide unique findings of brain function and organization under various motor recovery rehabilitation tasks after stroke.