The design removes the roof beam which obstructs the cabin on the 206/206L/407, and has an optional sliding main cabin door. The Bell 427's cabin is 13 in (33В cm) longer than the 407, and consists primarily of composite construction. Like the Bell 407, the 427 uses a four-blade main rotor system with a rigid, composite rotor hub and a two-blade tail rotor. The Bell 427 is powered by two Pratt & Whitney Canada PW207D turboshaft engines with FADEC. On January 24, 2008, Bell announced plans to officially discontinue its 427 line after current order commitments were fulfilled in 2010. In February 2005, the existing 80 orders for the 427 i were converted to the 429. However, the program was canceled and focus shifted to the improved Bell 429. The design had a fuselage lengthened 1В ft 2 in (0.36 m), a more powerful engine version and transmission, and increased takeoff weight.

The 427 i included a newer glass cockpit and navigation systems to allow single pilot flying under Instrument flight rules. The agreement gave KAI the development and production responsibility for the fuselage, cabin wiring, and fuel system. In 2004, Bell offered a redesigned 427 version, the Bell 427i, which was developed in partnership with South Korea's Korea Aerospace Industries and Japan's Mitsui Bussan Aerospace. The first customer deliveries occurred in January 2000. The 427's fuselage and tailboom are built by Samsung (later part of KAI) at its Sachon plant in South Korea. Bell builds the 427's flight dynamics systems at Fort Worth, Texas, while final assembly is performed at Bell's Mirabel, Quebec facility.

Canadian certification was awarded on November 19, 1999, followed by US certification in January 2000, and US FAA dual pilot IFR certification in May 2000. The Bell 427 first flew on December 11, 1997. The Bell 427 was the company's first aircraft designed entirely on computer. In February 1996, Bell announced its Model 427 at the Heli Expo in Dallas. The company began development of a new light twin, in partnership with South Korea's Samsung Aerospace Industries. However, Bell concluded that the payload-range performance of the 407T would not be sufficient. Bell's original concept for a replacement for the 206LT TwinRanger was the Bell 407T, a relatively straightforward twin-engine development of the Bell 407 with two Allison 250-C22B engines. Bell has tried several incarnations of a twin version of its successful Bell 206 series, including the stillborn Bell 400 and 440 in the mid-1980s, and the limited-production Bell 206LT TwinRanger in the early 1990s.

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