This study reports the direct observation of circularly polarized nonlinear optical activities in chiral hybrid lead halides (CHLHs), specifically R/S-DPEDPb₃Br₆·H₂O. The material exhibits high circularly polarized second harmonic generation (CP-SHG) efficiency, reaching up to 37% at room temperature, achieved through linearly polarized infrared light excitation. The unique zigzag inorganic framework reduces dielectric and exciton binding energy, enhancing spin polarization. The CP-SHG polarization ratio is attributed to strong spin-orbit coupling in the valence band and weak coupling in the conduction band, along with anisotropic noncentrosymmetric structure and reduced confinement effects. The study identifies two spin relaxation mechanisms: D'yakonov-Perel' (DP) and Bir-Aronov-Pikus (BAP). The DP mechanism dominates at high excitation fluence, while BAP is dominant at low fluence. Density functional theory analysis confirms strong spin-orbit coupling in the valence band and weak coupling in the conduction band, contributing to reduced spin relaxation and high CP-SHG polarization. The material also exhibits strong third harmonic generation (THG) and high laser damage thresholds, making it promising for optoelectronic applications. The study highlights the potential of CHLHs for advanced control of nonlinear optical polarization.This study reports the direct observation of circularly polarized nonlinear optical activities in chiral hybrid lead halides (CHLHs), specifically R/S-DPEDPb₃Br₆·H₂O. The material exhibits high circularly polarized second harmonic generation (CP-SHG) efficiency, reaching up to 37% at room temperature, achieved through linearly polarized infrared light excitation. The unique zigzag inorganic framework reduces dielectric and exciton binding energy, enhancing spin polarization. The CP-SHG polarization ratio is attributed to strong spin-orbit coupling in the valence band and weak coupling in the conduction band, along with anisotropic noncentrosymmetric structure and reduced confinement effects. The study identifies two spin relaxation mechanisms: D'yakonov-Perel' (DP) and Bir-Aronov-Pikus (BAP). The DP mechanism dominates at high excitation fluence, while BAP is dominant at low fluence. Density functional theory analysis confirms strong spin-orbit coupling in the valence band and weak coupling in the conduction band, contributing to reduced spin relaxation and high CP-SHG polarization. The material also exhibits strong third harmonic generation (THG) and high laser damage thresholds, making it promising for optoelectronic applications. The study highlights the potential of CHLHs for advanced control of nonlinear optical polarization.