The effect of incorporating ultra-dispersed diamond particles into the epoxy matrix of unidirectional carbon fiber reinforced polymer laminates was systematically examined. Laminates were produced by wet lay-up using a epoxy resin (EPICOTE 828) cured with an anhydride hardener (EPICURE), and the resin was modified with ultra-dispersed diamond at concentrations of 0, 0.01, 0.07, 0.10, and 0.20 weight percent. In the longitudinal direction, the tensile strength increased from 2316 MPa for the unmodified system to 2885 MPa at 0.20 weight percent, while the elastic modulus exhibited a maximum of 218.6 GPa at 0.01 weight percent before gradually decreasing at higher loadings. In the transverse direction, the absolute strength values were substantially lower and accompanied by higher scatter, whereas the modulus improved steadily from 6.2 to 7.5 GPa across the studied range. The results indicate that low levels of ultra-dispersed diamond reinforcement contribute to enhanced stiffness and strength through improved fiber–matrix interaction, while excessive additions promote particle agglomeration and diminish stiffness benefits. The overall findings identify the range between 0.01 and 0.10 weight percent as the most effective for achieving a favorable balance of strength enhancement and stiffness retention in carbon fiber reinforced polymer system.