The Jaguar XJ line received a facelift in Autumn 1973 for the 1974 model year, thereafter known as the Series 2; retrospectively the earlier cars were referred to as the Series I. The 4.2 L XJ6 straight-6 engine (most popular in the United Kingdom) and the 5.3 L V12 XJ12 were continued with an addition of a 3.4 L version of the XK engine available from 1975. The Series 2 and Series 2 coupé were the last Jaguar models with direct input by Sir William Lyons before his retirement.

Initially the Series 2 was offered with two wheelbases, but at the 1974 London Motor Show Jaguar announced the withdrawal of the standard wheelbase version: subsequent saloons all featured the extra 4 inches of passenger cabin length hitherto featured only on the long-wheelbase model. By this time, the first customer deliveries of the two-door coupe, which retained the shorter standard-wheelbase (and which had already been formally launched more than a year earlier) were only months away.

Series 2 cars are visually differentiated from their predecessors by raised front bumpers to meet US crash safety regulations, which necessitated a smaller grille, complemented by a discreet additional inlet directly below the bumper. The interior received a substantial update, including simplified heating and A/C systems to address criticisms of the complex and not very effective Series I systems.

The 1978 UK model range included the Jaguar XJ 3.4, XJ 4.2, XJ 5.3, Daimler Sovereign 4.2, Double-Six 5.3, Daimler Vanden Plas 4.2 and Double-Six Vanden Plas 5.3.