Twin-fluid atomizers are widely used in combustion systems, and a hybrid-mixed type that includes both internal and external atomizing air should be a promising twin fluid atomizer in order to freely control the spray atomization behavior, especially the near field breakup process. The present work is therefore focused on the near-field breakup characteristics of the liquid jet discharged from a hybrid-mixed twin fluid atomizer by use of the laser-based high-speed microscopic imaging technique. For the experimental work reported, the liquid injection pressure was fixed at 3.7 bar, and the flow rates of both internal and external mixing air were varied in the range of 0-90 standard liters per minute. Based on the near-field breakup characteristics, including the boundary of the main liquid jet, distribution of disintegrated ligaments/droplets, and near field droplet characteristics, the influence of atomizing flow rate and external swirl characteristics was investigated. The results show that the flow characteristics of internal/external air would alternatively dominate the flow structure of the main liquid jet and disintegrate parts at specific regions. Besides, the increase of both the internal and external flow rate would greatly enhance the We number of near field droplets by more than tenfold, and external swirl was also proved to be conducive to the breakup process. Finally, a near field surface mount device was successfully fitted to the flow rate of internal/external mixing air at both nonswirl and swirl conditions. These results provide important information for understanding and modeling the breakup characteristics of a hybrid-mixed twin fluid atomizer.