The Sunbeam 25 featured a 3619cc OHV six cylinder engine when launched for 1927. Following the usual Sunbeam practice of the time, it had a four speed gearbox with right hand change, semi-elliptic front suspension and cantilever rear suspension and a Claudel Hobson carburettor.
The chassis was based on that of the earlier Sunbeam 20/60. Bodies available were: Tourer, Rally Limousine, Enclosed Limousine, Enclosed Laundaulet and Weymann Limousine. The rally limousine was based on the bodywork of a 25 entered in the 1929 Monte Carlo rally.
In 1930, a vacuum brake servo was added and Stromberg carburettor fitted.
Production totalled around 1356 cars.