<p>This study investigates the hydro-mechanical properties of biochar-amended cracked soils and their impact on slope stability under climate change. The laboratory tests analyzed the saturated water permeability (<i>k</i>_<i>s</i>), soil water retention curve (SWRC) and shear strength of biochar-amended cracked soil during dry–wet cycles. Numerical simulations were conducted based on the laboratory test results to evaluate the stability of biochar-amended cracked soil slopes under infiltration conditions, using Monte Carlo simulations. The test results demonstrate that biochar amendment significantly reduces the crack ratio, with biochar pyrolyzed at 200&#xa0;°C decreasing it by 40.8% and 500&#xa0;°C biochar by 35.7%. 500&#xa0;°C biochar demonstrates greater advantages in enhancing hydro-mechanical properties of soil. 500&#xa0;°C biochar reduces permeability degradation by 20% and improves water retention capacity by 25%. The numerical results reveal that increasing the crack ratio from 0 to 9.8% reduces the factor of safety (FOS) from 1.70 to below 1.0. Variations in crack depth and spacing alter water flow paths and pore water pressure (PWP) distribution, inducing FOS fluctuations by up to 40%. Biochar amendment significantly enhances slope stability during rainfall events, resulting in a 41.7% increase in FOS under worst-case conditions (9.8% crack ratio, 2&#xa0;m crack depth, and 0.5&#xa0;m crack spacing). The biochar-amended soil (BAS) slope demonstrates enhanced reliability, with the probability of instability under worst-case conditions decreasing substantially from 89.6% to 0.3%. This study implies that biochar amendment effectively improves the stability of slopes with cracks under dry–wet cycles and rainfall infiltration.</p>