This study experimentally investigated the effect of partially replacing fine aggregate with stone dust and brick dust in concrete. Concrete mixtures were prepared by replacing fine aggregate with stone dust and brick dust from 0% to 25% at increments of 5%. Samples were tested to determine workability and compressive, split tensile, and flexural strengths at 7, 14, and 28 days. Results showed that stone dust and brick dust improved concrete strengths up to 20% replacement, with maximum improvements of 24%, 26%, and 18% for compressive, split tensile, and flexural strengths respectively. Strengths decreased with 25% replacement. It was concluded that 20% replacement of fine aggregate with stone dust and brick dust is optimal.