Globally, the generation of Waste Asphalt Pavement (WAP) is increasing rapidly. To address this, the Government of Bangladesh has targeted incorporating 25% WAP in road construction by 2025. This study evaluates the mechanical performance and sustainability potential of WAP blended with Crushed Stone Aggregates (CSA) and stabilized using Hydrated Lime and Sawdust Ash (SDA) for sub base applications in flexible pavements. Eight laboratory mix designs were prepared by varying CSA and WAP contents. Specimens were compacted at optimum moisture using the Modified Proctor method, and performance was assessed through Aggregate Crushing Value (ACV) and California Bearing Ratio (CBR) tests. All blends exhibited strong resistance to crushing, with ACV values ranging between 16% and 17.93%, well below the 25% limit for sub base materials. The CBR results were as follows: 75% CSA + 25% WAP + 3% Lime (9.67%), 75% CSA + 25% WAP + 6% Lime (11.75%), 50% CSA + 50% WAP + 3% Lime (11.40%), 50% CSA + 50% WAP + 6% Lime (17.46%), 75% CSA + 25% WAP + 3% SDA (51.75%), 75% CSA + 25% WAP + 6% SDA (58.75%), 50% CSA + 50% WAP + 3% SDA (38.39%), and 50% CSA + 50% WAP + 6% SDA (29.46%). SDA-stabilized mixes achieved the highest CBR values, confirming superior strength gain, while lime offered improved load-bearing capacity at a lower cost. The study concludes that WAP with proper stabilizers can deliver durable, cost-effective, and sustainable sub base layers for road construction in Bangladesh.