BMW needed to expand its model range, but they did not have the resources to develop an all-new car with an all-new engine. Therefore, it used the Isetta as starting point for a new four seat economy car.

As a result, the 600 used the front suspension and front door of the Isetta. The need to carry four people required a longer frame, a different rear suspension, and a larger engine. A new perimeter frame was designed, using box section side members and straight tube crossmembers. The rear suspension was an independent semi trailing arm design; this was the first time BMW had used this system. The chassis had a wheelbase of 1,700 millimeters (67 in), a front track of 1,220 millimeters (48 in), and a rear track of 1,160 millimeters (46 in).

The 600 was powered by the 582 cc (35.5 cu in) flat-twin engine from the R67 motorcycle/sidecar combination. This engine, which delivered 19.5 horsepower (14.5 kW) at 4,500 revolutions per minute, was mounted behind the rear wheels. A four-speed manual gearbox was standard, while a Saxomat semi-automatic transmission was available. The 600 had a top speed of approximately 100 km/h.
Access to the rear seats was by a conventional door on the right side of the vehicle.