The DB3 was introduced in 1951 with a 133 hp 2.6-litre Lagonda straight-six engine taken from the DB2 Vantage. Development was complicated from the outset: a new V12 engine had been considered for the car, but funds had to be directed instead toward making the DB3 competitive. The car's early results were modest, and a larger 2.9-litre engine producing 163 hp was introduced in June 1952.
At Silverstone in May 1952, DB3s in 2.6-litre form finished second, third, and fourth, beaten by a Jaguar C-Type. The works cars were forced out of Le Mans without a result that year, but the team did claim victory in the nine-hour race at Goodwood.
In 1953 the DB3 produced its most significant result when a car driven by Parnell and Abecassis finished second at the Sebring 12 Hours — the opening round of the World Sports Car Championship — behind a Cunningham CR4. At the second round of the championship, the Mille Miglia, Reg Parnell drove a DB3 to fifth place, described as the highest position ever reached by a British sports car in that Italian classic.
A total of ten DB3 chassis were built between 1951 and 1953, numbered DB3/1 through DB3/10. Chassis numbers 1 to 5 were used as works cars; numbers 6 to 10 were sold to customer teams. Chassis DB3/1 was sold to Eric Forrest Greene in 1953. He entered it once, at the 1954 1000 km Buenos Aires, where the car crashed and caught fire, fatally injuring the driver. The repaired chassis was subsequently raced by his son Jack.
Several DB3 chassis later received coupé bodywork, becoming distinctive one-off variants raced in period events and preserved in later decades.
The DB3S, introduced in 1953, was a lighter evolution of the DB3. Two works coupé versions were built alongside the standard open-car configuration. The DB3S proved more successful in competition than its predecessor and remained Aston Martin's front-line racing car until 1956, when it was replaced by the DBR1. The DBR1 went on to win the 24 Hours of Le Mans in 1959, providing the culmination of the competitive programme that the DB3 and DB3S had initiated.
The DB3 programme represented Aston Martin's most serious attempt to compete at the top level of sports-car racing during the early 1950s. Despite a difficult beginning, the results at Sebring and the Mille Miglia in 1953 established the team's credentials in international endurance competition. The lessons learned informed the development of the DB3S and ultimately the DBR1, which brought Aston Martin its greatest racing success of the era.