Fatigue crack growth behavior of Al 7075-T6 alloy was investigated under in-plane biaxial fatigue loading with mixed-mode overloads. Cruciform geometry specimens were tested with specially programmed load spectra having single mixed-mode (mode I+II) overloads within a constant amplitude pure mode-I baseline load spectrum. The effects of mixed-mode overloads of different magnitudes on crack retardation behavior and crack growth micromechanisms were studied in detail by correlating the macroscale crack growth rates with fracture surface morphology through quantitative fractography. The retardation effects were found to increase with overload ratio and with the instantaneous fatigue crack at the instance of overload. Mode-mixity induced crack closure mechanisms played a dominant role in crack retardation for shorter cracks while mode-I plasticity induced crack closure was observed to be the dominant mechanism in the case of longer crack lengths.