The high environmental impact and cost of cement-based construction materials have intensified the search for sustainable alternatives. This study investigates the mechanical, durability, and microstructural performance of compressed stabilized earth blocks (CSEBs) incorporating Parkia biglobosa (Makuba) as a bio-based stabilizer. Lateritic soil was characterized using particle size distribution, Atterberg limits, and compaction tests, while Makuba extract was chemically analyzed. Blocks were produced with varying Makuba contents and cured for 7–28 days. Compressive strength, water absorption, and microstructural properties (SEM, EDX, XRD) were evaluated. Results show strength improvements of 25–60%, with peak values exceeding 3.0 N/mm², satisfying Nigerian Industrial Standard requirements. Water absorption decreased by 15–35%, remaining below 12%, while microstructural analysis revealed pore refinement, enhanced particle bonding, and matrix densification. The findings confirm Makuba as a viable low-cost, eco-friendly stabilizer capable of producing durable structural earth blocks suitable for sustainable housing applications.