The surface passivation is an important technique that suppresses the effects of surface dangling bonds on the one-dimensional (1D) nanostructure and changes their electronic properties due to the elimination of surface states. Hydrogen (H) is one of the most renowned surface passivants that can effectively passivate the dangling bonds on the surfaces of group IV materials such as carbon (C), silicon (Si), and germanium (Ge). In this paper, the sp(3) tight binding calculation has been performed to investigate the effects of surface passivation by H atoms on the structural and electronic properties of a germanium nanowire (GeNW) oriented along < 100 >, < 110 > and < 111 > crystallographic directions over a wide diameter range. The results show that when the entire surface dangling bonds of a GeNW are passivated with H atoms both the nature and magnitude of the band gap are tailored for each diameter and growth direction. Without H passivation of GeNWs surfaces, (i) the < 100 >-oriented GeNW show indirect band gap semiconductors nature for all diameter values with magnitude of band gap is smaller than the band gap value of a Bulk Ge, (ii) the first smaller diameter < 110 >-oriented GeNW show zero band gap semiconductor (metallic in nature) while for all the others diameter values they exhibit indirect band gap semiconductors nature with magnitude of band gap is smaller than the Bulk Ge, and (iii) the first smaller diameter < 111 >-oriented GeNW show indirect band gap semiconductor nature while the two show zero band gap semiconductors (metallic) as well as the others three exhibits narrow direct band gap semiconductors. Further analysis show that when the surface of a GeNW are passivated by H atoms, all the < 100 >-oriented, < 110 >-oriented, and < 111 >-oriented GeNWs exhibits direct band gap semiconductors nature with a magnitude of band gap inversely proportional to their diameter. This shows that the magnitude of band gap for each oriented H passivated surface GeNW is larger at smaller diameter which further decreases with the increase in their diameter and approaches the band gap value of a Bulk Ge at a larger diameter value. These results confirm the suitability of an H-passivated GeNW for designing high quality nanoelectronic devices and for optoelectronic applications particularly for making optical devices such as light emitting diodes and semiconductor lasers.