The present study is of formulation and evaluation of Atazanavir co-crystals to improve drug oral bioavailability. Atazanavir co crystals were prepared by sovent evaporation technique using Oxalic acid, succinic acid, saccharin, were as co crystal formers, various formulations were prepared these polymers. The Atazanavir co-crystals were characterized with respect to IR, DSC, XRD, angle of repose, bulk density, tapped density, Carr’s index, Hausner’s ratio, and stability studies and all the results indicated that the co-crystals were having good flow nature. Conclusion: By the in vitro dissolution studies it was concluded that the formulation prepared with oxalic acid in the concentration of 200mg (F4) was showing better result 98.97% drug release.