Separation control and formation of boundary layer Newtonian flow in a diverging perme-able channel in Darcy-Forchheimer porous material having suction/injection are discussed. Self-similar equations from governing equations are acquired and existence conditions for boundary layer structure are derived using nature of velocity gradient inside boundary layer. It reveals that if sum of Darcy permeability parameter and twice of Forchheimer parameter exceeds 2, then the boundary layer flow always exists with all type of mass suction/injection and even without suction/injection. Also, if mass suction parameter goes beyond 22, then there is no matter what are the values of Darcy permeability parameter and Forchheimer pa-rameter, a boundary layer exists inside the divergent channel. In addition, obtained numerical solutions are exhibited graphically. It reveals that thicknesses of velocity and thermal bound-ary layers reduce with Darcy and non-Darcy resistances of porous medium and fluid tempera-ture also diminishes. The velocity and temperature reduce with increment of mass suction and contrary results are found for mass injection.