Standard compact tensile (CT) samples were tested to compare the fatigue crack growth rates (FCGRs) of the arc dominated zone (ADZ), laser dominated zone (LDZ), heat affected zone (HAZ), and base metal (BM), which were sampled on the laser arc hybrid welding joints of an ultra-low-carbon bainitic steel. The growth features of the fatigue crack in each microcell were summarized, and the reason for the deflected path of crack growth was explained. The result shows that the FCGRs increase but the accelerated velocities of the HAZ and BM decrease with the growth of the stress intensity factor (SIF). At the low SIF, the FCGRs decrease in the following sequence: BM, HAZ, ADZ, and LDZ. When the SIF is sufficiently large, the sequence changes to: LDZ, ADZ, BM, and HAZ. The crack-path deflection in the HAZ is observed clearly, and the secondary cracks increase when the SIF increases. However, the crack deflection in the weld zone is not observed clearly. This difference is attributed to the non-uniformity in the material composition and microstructure. The observation of the fracture explains that the generation of the secondary cracks is associated with the brittle phases. Further, the secondary cracks are primarily responsible for the change in the FCGRs.