The B6 3.5 was introduced in 1984 as the big brother to the B6 2.8/1. The B6 3.5 was also based on the E30 325i however utilized the even bigger 3.5 liter six cylinder engine.

Alpina modified the cylinder-head and combustion chambers, fitted lighter, higher-compression Mahle pistons, a new camshaft and a new exhaust system to increase power from 218hp to 261 bhp. Torque increased to 346 Nm. With catalyst the power only decreased by 3% to 254 bhp.

The standard gearbox is replaced by a Getrag 5-speed gearbox.

The suspension was replaced with Bilstein units with stiffer gas-pressure shocks and progressive springs at front.

The front brakes were upgraded with bigger, ventilated discs.

The trademark Alpina-wheels are 16in high and 7in wide with 205/50 tires all-around.

The seats have been replaced with Recaro bucket seats with Alpina stripes. The steering wheel is leather-covered. The speedo has been replaced and there are new digital instruments mounted in the air vents in the center of the dashboard. The exterior changes include a new front spoiler, rear spoiler, the wheels and optional Alpina stripes.

Alpina claimed 0-100 km/h in 6.4 seconds and a top speed of 250 km/h. But according to Auto Motor und Sport´s test the B6 3.5 could accelerate from 0-100 km/h in only 6.0 seconds, 0-160 km/h in 14.6 seconds, 0-200 km/h in 26.2 and had a top speed of 253 km/h.

For the catalyst version, Alpina claimed 6.6 seconds from 0-100 km/h and a top speed of 246 km/h. But once again Auto Motor und Sport´s test showed that the car was faster than claimed.

The B6 3.5 was built from August 1984 until December 1990. From 1986 the B6 was optionally available with catalyst until July 1987 when the non-catalyst B6 3.5 was no longer offered. Production ended in December 1990.

A total of 219 cars were built.