We have investigated the atomic structure and electronic states of the Si(111)-(4×1)In surface using the first-principles total energy calculations. The atomic coordinates optimized for this surface are in excellent agreement with those obtained from the recent x-ray diffraction experiment [Bunk et al., Phys. Rev. B 59, 12 228 (1999)]. The calculated surface electronic structure, which is anisotropic, provides a satisfactory description of angle-resolved photoemission data. These calculations provide strong support for the model proposed by Bunk et al.