An internal mix spray nozzle assembly adapted for operation with lesser pressurized air requirements. The spray nozzle assembly includes a liquid passage for directing a liquid flow stream against an impingement pin, and an air guide is provided for forming an annular pressurized air passage about the liquid flow stream for striking and atomizing a laterally spreading dispersion of liquid from the impingement surface. For enhancing liquid atomization, the air guide defines a relatively narrow width air flow opening for substantially accelerating and increasing the pressure of the atomizing air stream, and the impingement pin is formed with a relatively large primary impinging surface and a parallel downstream secondary impingement surface that facilitates further liquid particle breakdown and prevents the accumulation of liquids about the bottom of the impingement pin.