In recent past, W.A.Hiscock [ Class.Quan.Grav. (1990) 7,6235 ] studied the semi classical gravitational effects around global monopole. He obtained the vacuum expectation value of the stress-energy tensor of an arbitrary collection of conformal mass less free quantum fields (scalar, spinor and vectors) in the space time of a global monopole. With this stress-energy tensor, we study the semi classical gravitational effects of a global monopole in the context of Brans-Dicke theory of gravity.