This paper describes an experimental study of the behaviour of spray structure in an internally mixed, twin fluid atomizer in which air was introduced tangentially into the liquid stream inside the atomizer. The atomization in such atomizers is perceived to be strongly influenced by the mass flow ratio of atomizing gas (air) and the liquid (water). The order of magnitude of the ALR (Air-liquid mass flow ratio), for which the study was conducted, ranged from 0.0277 to 0.623. A PDPA (Phase Doppler Particle Analyzer) was used to study the spray formation process. The behaviour of the spray was studied by velocity and Sauter Mean Diameter (SMD) variations at a plane normal to the spray axis as well as along the flow direction of the atomizer. It was observed that the mass flow rate of the liquid deceases with an increase in air pressure while it increases with liquid pressure. The droplet diameter decreases with an increase in ALR for a given liquid supply pressure but sprays having droplet SMD of less than 60 mu m at the centerline of the spray was produced at relatively lower ALR (i.e., 0.1). The variation demonstrated by the atomizer in this study makes it flexible to be used for various commercial applications, as the atomizer is capable of providing a wide range of spray patterns depending upon the application requirement.