In 1947, David Brown purchased the Aston Martin and Lagonda companies, incorporating them as Aston Martin Lagonda Ltd. Brown's main objective in acquiring Lagonda was its 2.6 L (2580 cc/157 in3) dual overhead cam straight-six engine, which was more powerful than the 2.0 L straight-four in the Aston Martin 2-Litre Sports. W. O. Bentley supervised the engine's design, which was largely carried out by William (Willie) Watson, an engineer who had collaborated on Lagonda's pre-war V12 and designed the short-lived post-war version.
In its original form, the Lagonda straight-6 had a 78 mm (3.07 in) bore and 90 mm (3.543 in) stroke, producing about 105 hp (78 kW) with dual SU carburettors. The DB2 utilized a shortened version of the tube-frame chassis designed by Claude Hill for the Aston Martin 2-Litre Sports, with a fastback coupé body designed by Frank Feeley.
Three pre-production cars were entered for the 1949 24 Hours of Le Mans. One car, which would become the development car for the production DB2, was equipped with the Lagonda straight-6, while the other two used the four-cylinder Aston Martin 2-litre unit. The Lagonda-powered car, driven by Leslie Johnson, retired after six laps due to overheating caused by a water pump failure. One of the 2-litre cars crashed two hours before the finish, fatally injuring driver Pierre Maréchal, after running without brakes. The other 2-litre car finished 7th, crewed by Arthur Jones and Nick Haines. A month later, the larger-engined car, driven by Leslie Johnson and Charles Brackenbury, finished 3rd in the Spa 24-hour race. One of the 2-litre cars was driven to 5th by Nick Haines and Lance Macklin in the same race.
For 1950, all three factory team cars were equipped with the Lagonda engine. At the 1950 Le Mans race, the car driven by George Abecassis and Lance Macklin finished 5th, with Brackenbury and Reg Parnell bringing another home 6th, securing 1st and 2nd in the 3-litre class for Aston Martin. In the United States, Briggs Cunningham drove his DB2 to 2nd in its class at the inaugural Sebring race meeting in December 1950. The factory team cars continued racing in Europe throughout 1951, including at Le Mans, where Macklin and Eric Thompson took 3rd overall, with Abecassis and Brian Shawe-Taylor finishing 5th. Following these races, David Brown began developing Aston Martins specifically for competition use, starting with the DB3.
The DB2 debuted at the New York Auto Show in April 1950 and continued in production until April 1953. The first 49 cars had a chrome-framed front grille in three separate parts and large rectangular cooling vents in the front wings. Subsequent cars featured a one-piece grille with horizontal chrome slats and no side vents. The single-piece bonnet was hinged at the front. At the rear of the fixed-head coupé (FHC), a small top-hinged lid provided access to the spare wheel, and luggage space was located behind the front seats, accessible only from inside the car.
Later in 1950, a Drophead Coupé (DHC) variant was introduced, with at least 102 units built. In April 1950, an engine upgrade option, Aston Martin's first Vantage, was made available. This option offered 125 hp (93 kW) through larger carburettors, an inlet camshaft with increased duration (the same as the exhaust camshaft), and higher compression ratio pistons (8.16:1). Initially, the higher compression ratio made the engine unsuitable for the British market due to post-war austerity measures that restricted UK vehicles to 72 octane "Pool petrol." The first DB2 Vantage, LML 50/21, was delivered to and raced by Briggs Cunningham in the United States.
A closed coupé tested by the British magazine The Motor in 1950 achieved a top speed of 116.4 mph (187.3 km/h) and could accelerate from 0-60 mph (97 km/h) in 11.2 seconds. A fuel consumption of 20 miles per imperial gallon (14 L/100 km; 17 mpg‑US) was recorded. The test car cost £1914 including taxes.