It was the first model produced by SEAT, and the first car to be assembled at the firm's then-new plant located in Barcelona's Zona Franca zone.

Initially, components were shipped as CKD kits from Italy and assembled by SEAT at their plant in Zona Franca, but in 1954 the Spanish-made parts content rose to a 93% proportion of the total in order to limit imports and to help the development of the almost non-existent Spanish supplier industry, thus fulfilling SEAT's assigned key role in the development of the Spanish economy as the national car maker of the post World War II Spain.

The first SEAT 1400, offered between 1953 and 1955, incorporated a 1395 cc four-cylinder water-cooled Fiat engine with a claimed output of 44 bhp and top speed of 120 km/h (75 mph).

The SEAT 1400 A, the first revision, launched for 1955 was a modernised version of the original 1400, based on the Fiat 1400 A which had appeared from Turin the previous year.

Announced at the end of 1956, the SEAT 1400 B appearing for 1957 retained its predecessor's bodywork but featured a revised front grill and offered a two tone paint scheme.