An experimental investigation of the primary breakup and spray characteristics of a rotary atomizer with round radial discharge channels operating in the Coriolis-induced stream-mode injection was conducted. A high-magnification shadow imaging technique with pulsed backlight illumination was used for spray visualization. The effect of the rotational speed and volume flow rate variations was studied on the breakup structure. The length of the rotary atomizer's discharge channels is long enough to accumulate the liquid film on one side of it due to the Coriolis acceleration. The observations showed that the liquid stream issues from the atomizer orifice as a liquid column or a thin liquid sheet depending on the atomizer operating condition. It was found that the aerodynamic Weber number and Coriolis Bond number determine the state of the initial liquid stream. Different breakup modes such as Rayleigh, bag, column, ligament, and shear breakup were observed. A breakup mode map is presented based on two nondimensional parameters, the aerodynamic Weber number and the liquid-to-air momentum flux ratio. The breakup mode map was compared with the results obtained in the previous study for the radial-axial type of discharge channel. The results indicate that the orientation of the discharge channel with respect to the radial direction can affect the breakup modes in an aerodynamic Weber number less than 30. To evaluate the spray quality of this type of atomizer, the droplet size and Sauter mean diameter (SMD) value have been measured at different operating conditions by the particle/droplet imaging analysis (PDIA) technique. The results indicate that the droplet size primarily depends on the Weber number and liquid-to-air momentum flux ratio.