The genus Sporobolus (Poaceae Chloridoideae) consists of approximately 160 species of tropical and subtropical grasses. In Brazil, this genus is represented by 28 species, among which Sporobolus indicus stands out, a perennial species, made up of two varieties (indicus and pyramidalis), distributed throughout the national territory. In a 1979 botanical survey, in degraded pastures, in the northeast (Paragominas) and south (Santana do Araguaia) of the state of Pará, Brazil, Sporobolus indicus is not listed as a frequent species, although it is present in Santana do Araguaia. That said, this work aims to present a study on a polyester composite reinforced by Sporobolus indicus fibers. The composites were manufactured with fiber in different lengths, 5, 10 and 15 mm, added discontinuously. A tensile test was carried out following the ASTM D 638M standard. A composite of the same matrix was also manufactured with the aforementioned fiber, unidirectionally aligned. The tensile test was carried out according to the ASTM D 3039 standard, in order to compare results. It was possible to notice the behavior of the composite by varying the length of the reinforcement introduced into the matrix. The mechanical resistance showed growth proportional to the growth of the fibers, with the values found for the composite reinforced with discontinuous fibers being 11.33, 12.10 and 14.95 MPa, respectively, in increasing order according to the size of the fibers, while the results for the specimens reinforced with unidirectionally aligned fibers were 18.84 MPa. This occurs due to the alignment of the reinforcement within the mold, where in a length of 5 mm, many fibers were arranged transversely to the direction of application of the load on the specimen, not cooperating with the resistance and causing failure mechanisms. At a length of 15 mm, the fibers were distributed longitudinally in the center of the specimen, coinciding with the direction of load application and enabling greater tensile strength.