Bianchi type - V space time is considered in the presence of perfect fluid source in the scalar - tensor theory of gravitation proposed by Brans and Dicke [Phys. Rev.124, 925,1961]. With the help of special law of variation for Hubble’s parameter presented by Bermann [Nuovo Cimento B74, 182, 1983] a cosmological model with negative constant deceleration parameter is obtained in the presence of perfect fluid with disordered radiation. Some physical and kinematical properties of the model are also discussed.