Due to rampant urbanization and rapid construction industry growth, the structures are being laid upon a weak foundation medium. Thus, it becomes necessary to enhance/modify the strength and serviceability of the weak soil medium. The clayey soil, such as black cotton soil, is weak in strength compared to sandy soil, and it becomes susceptible to cracking when the moisture content is reduced due to volume change. The purpose of this study is to introduce randomly dispersed polypropylene fibres and nano-silica to black cotton soil in order to increase its undrained shear strength. To increase the soil’s undrained shear strength, varying percentages of polypropylene fibres, nano-silica, or a mix of the two are considered, depending on the dry weight of the soil. To determine the undrained shear strength, the unconfined compressive strength (UCS) is measured on a total of 80 test samples. The addition of nano-silica is observed to enhance the UCS, due to enhanced bonding, and the same is found to be increased with increase in curing time and imparted brittle failure. Furthermore, by the addition of randomly distributed polypropylene fibre, the brittle nature is reduced. The UCS of the samples is found to be enhanced when the inclusion of polypropylene fibres is made; it increases by 4%, 67%, 94%, 118%, and 213% for 1%, 2%, 3%, 4%, and 5%, respectively. The same increases by 87%, 111%, 187%, 208%, and 231% for 1%, 2%, 3%, 4%, and 5%, respectively, after 14 days of curing with nano-silica addition.