The 340 is a six seat aircraft, with four passenger seats, an aisle and an air stair door. The tail and landing gear were based on the Cessna 310's units, while its wings were from the Cessna 414. The 340's primary selling features were its spacious, pressurized cabin, the first in a light twin.

Work on the 340 began in 1969 and the first aircraft was delivered in 1971, behind schedule as one of the prototypes crashed during flight testing in 1970.

The early models have two turbocharged Continental TSIO-520-K engines with 285 hp (214 kW) each. Starting in 1976 the engines were upgraded to the more powerful Continental TSIO-520-NB engines of 310hp (233 kW). This variant is known as the 340A and it also features smaller 75.5 inch diameter propellers to reduce noise and meet ICAO Annex 16 noise requirements.