The experimental study investigates the influence of biochar addition on the mechanical properties of sand, focusing on the behaviour observed in the Consolidated Undrained (CU) static triaxial shear test. Triaxial shear tests were conducted on biochar contents varying from 1 to 40% dry weight of pure sand. The introduction of biochar led to a reduction in density, attributed to its lightweight nature. On the other hand, deviator stress showed an elevation with increasing biochar content; it peaked at 20% biochar before declining. The interaction between the biochar and the sand has influenced the stress–strain characteristics of biochar-amended sand, and it was mobilized at higher strain levels. Further, the addition of biochar demonstrated the potential to improve the dissipation of pore pressure, especially at 20% biochar. The dissipation rate decreased with increasing biochar percentages above 20%.