A series of noncentrosymmetric (NCS) tetraethy-lammonium tetrahalide indium hybrids, [(C2H5)(4)N]InCl(4-x)Brx (x = 0, 2, 4), was synthesized by a hydrothermal reaction. Their structures, thermal properties, and linear and nonlinear optical properties were identified. The crystals belong to an isomorphic hexagonal system and feature zero-dimensional structures containing isolated distorted InCl4-xBrx- tetrahedra with [N(C2H5)(4)](+) cations inserted as charge balance. On the basis of the powder second harmonic generation, the SHG levels of [(C2H5)(4)N]-InCl4-xBrx (x = 0, 2, 4) were estimated to be approximately 0.5, 0.7, 0.8 X KDP, respectively. The relationship between halogen composition and band gap, optical anisotropy, and frequency doubling effects were evaluated by first-principles calculations, thus suggesting that halogen regulation favors the design of new organic-inorganic hybrid halides with excellent performances for many optoelectronic applications.