Alpina B4 S Edition 99 at the 2019 Geneva Motor Show

Introduced in October 2018, the B4 S Edition 99 is a limited edition of the B4 S limited to 99 units. The 99 Edition received further engine upgrades and generates 458 PS (337 kW; 452 hp) between 5,500 and 6,250 rpm and 680 N⋅m (502 lb⋅ft) of torque between 3,000 and 4,500 rpm from its 3.0-litre twin-turbocharged straight six engine. The coupé with all-wheel-drive weighing 1,750 kg (3,858 lb) accelerates to 100 km/h (62 mph) from a standstill in 3.9 seconds and the 65 kg (143 lb) lighter rear-wheel-drive coupé accelerates to the same speed in one-tenth of a second longer than the all-wheel-drive coupé. The convertible accelerates to the same speed in 4.3 seconds. All of the versions have a top speed ranging from 303–306 km/h (188–190 mph).

Two new colour options are available for the exterior, those being Fire Orange and Grigio Medio with black accents. A matte wrap is available as an option. The car is available with 20-inch classic Alpina multi-spoke alloy wheels in Ferric Gray finish.

The Edition 99 has a stiffer suspension system than the B4 S called the Alpina Sports Suspension Plus along with modified adjustable dampers. A limited slip differential and a torque vectoring system is available as an option. The interior features piano black lacquer trim with "Edition" lettering, new sports seats, the shift paddles finished in matte black and a stainless steel plaque signifying the production number of the car out of the 99 units produced.