We have investigated third order nonlinear optical properties and spectral characteristics of methylene blue dye in both polymer and liquid mixtures. The spectral characteristics of the dye is studied by recording the absorption and fluorescence spectra of the dye doped in poly(methylmethacrylate) modified with additive n-butyl acetate(nBA) and the dye in MMA and nBA (liquid mixture). The spectral results of the dye doped polymer rod are compared with dye in liquid Mixture. The nonlinear measurements of the dye in liquid and polymer medium were performed using CW He-Ne laser of wavelength 632.8 nm by employing z-scan technique. The dye methylene blue showed a negative nonlinear refractive index.