The recent decline in asphalt pavement longevity has created problems like irreversible deformation or rutting. Adding sisal fibres to asphalt layers can improve pavement performance and reduce maintenance needs. This paper aimed to investigate the potential effects of sisal fibres on pavement performance. Modified asphalt mixture samples were prepared for laboratory testing using asphalt cement of grade 40–50 from the Durah refinery. Asphalt layers containing sisal fibres were compared with those without. Samples were created by adding 0.2%, 0.3%, and 0.4% fibres by weight to the asphalt. To assess sustainability, the effect of fibre modification was estimated using mensuration such as wheel track, Indirect Tensile Strength, and Marshall Stability. The results indicated that the ideal fibre content for maximum strength and scratch-resistance in the mixture is when the Marshall Stability is about 0.2% on the x-axis, which is its highest peak. In addition, the Marshall flux grows linearly on the x-axis with a value of 5.0 (about 3.4%). Sisal fibres also increased Indirect Tensile Strength, with the highest strength recorded at 0.2% fibre content (1.03 MPa), compared to 0.42 MPa for the unmodified mixture. Thus, the addition of sisal fibres in specific amounts improves the stability of asphalt and optimises the mixture’s performance. They can be used to prolong pavement performance by increasing flexibility and decreasing deformation in the long run.