A series of bithienyl azo dyes has been prepared from their corresponding coupling components, 5-alkoxy-2,2´-bithiophenes. The solvatochromic behavior of the compounds was investigated. The hyperpolarizabilities β of derivatives 3-5 were measured using hyper-Rayleigh scattering and thermogravimetric analysis (TGA) was used to evaluate their thermal stability. The experimental results indicate that, good nonlinearity-thermal stability is well balanced for azo-bithiophene NLO-chromophores 3-5 making them good candidates for NLO applications.