In spray systems, swirl motion is generally imparted to the liquid jet in order to favor its fragmentation. In coaxial atomization applications, however, due to its higher momentum, the dynamics of the flow is controlled mainly by the annular gas jet. As a consequence, we examine the effect of a swirling coaxial gas jet on breakup and atomization of a liquid jet as a function of the rotation intensity, given by the swirl number S, gas-to-liquid momentum flux ratio J, and surrounding pressure. The main results were: low enhancement of the atomization with no major changes of the jet development for low swirl, but, when a critical amount of rotational flow is imparted to the gas stream according to experimental conditions, topology of the flow is significantly modified. This transition leads to a significant decrease in liquid jet breakup length and an inversion of droplet distribution. The second kind of flow is linked with the appearance of a stagnation point on the jet centerline, whose occurrence and characteristics depend on operating conditions.