Shear strength behavior of expansive soil reinforced by randomly placed fiber depends on the added materials’ content. This research investigated the effect of the waste coconut fibers content on the stress-strain relationship, the shear strength parameters, and the mixture’s elastic modulus. In this study, the coconut fiber content was varied from 0.25% to 1% with 0% fiber as control. The clay samples were tested after mixing by unconsolidated-undrained triaxial test. In general, according to the test result, the inclusion of randomly placed waste coconut fiber has enhanced the peak deviatoric stress, the shear strength parameters, and the elastic modulus. At 0.6% fiber content, the shear strength and the samples’ elastic modulus have increased to 79.46% and 153%, respectively, compared with those not reinforced with coconut fiber.