Announced in May 1957 the XK150 had a familiar resemblance to the XK120 and XK140, but has been radically revised. Visibly, a one-piece windshield replaced the split screen, and the wing line was higher and more aerodynamic on the doors. The extended hood opened to the wings and, in the coupés, the windshield structure was moved forward, 102 mm, to facilitate the access of passengers. The car was available on several occasions in red, pearl gray, white, indigo blue, claret, Cotswold blue, black, fog gray, Sherwood green, Carmen red, British Racing Green, Cornish Gray and Imperial Maroon.

The XK140's walnut panel has been replaced with a leather trim. In the first tilting coupés, the central aluminum panel, which was discontinued after June 1958, had an X-patterned engraving similar to the beginning of the E-Type 3.8. Thinner doors gave more interior space. A small red light reminded the driver that the front parking lights, located on top of the wings (fenders), were on.

The suspension and chassis were very similar to the XK140, with rack and pinion steering only manual. The 3.4-liter DOHC straight-6 XK engine was similar to that of the XK140, but a new type "B" head increased power to 180 SAE bhp at 5750 rpm.

XK150 S 3.4L XK engine with orange paint used on S models with "straight door" heads equipped with three carburetors

The first closed and convertible XK150s were slower than their predecessors. After a twelve-month delay caused by the factory fire in February 1957, this deficit was corrected in the spring of 1958 with the launch in March of special equipment models equipped with disc brakes and a more powerful SE engine. Two 1.75 ”SU HD6 carburetors (44 mm) and a modified type B cylinder head with larger exhaust valves improved performance to 210 hp at 5500 rpm. While most export cars were SE models, a third option for the open two-seater car included an "S" engine with three 2-inch (51 mm) SU HD8 carburetors and a straight-door cylinder head that drove 250 SAE bhp.

In 1960, the 3.8-liter, 220 hp (223 hp; 223 hp) engine, installed in the luxurious Mark IX salon, since October 1958, became available. [6] It was tuned to produce 265 hp (198 kW; 269 PS) and propel an XK150 at 135 mph (217 km / h) and from 0 to 60 mph in about 7.0 seconds. Fuel economy was 18mpg. [4] Dunlop 12-inch (305 mm) four-wheel disc brakes first appeared as an option. Factory specifications 6.00 × 16 inch Dunlop Road Speed tires or optional 185VR16 Pirelli Cinturato CA67 radials could be mounted on 16 × 5K½ solid wheels or optional 16 × 5K wire wheels.