A twin turboprop-powered version of the radial-engined P-2 Neptune, the P-2J was developed as an alternative to buying the larger and more expensive P-3 Orion, which would eventually replace the P-2J in the 1980s.

The Kawasaki-built P-2J (originally P2V-Kai, where "Kai" (改) means modification) was the last version of the Neptune to be produced.

[3] The Ishikawajima-Harima J3-IHI-7C booster turbojets, produced 13.7 kN (3,085 lbf) thrust, giving the P-2J a top speed of 650 km/h (400 mph).

[3] The forward fuselage was extended 4 feet 3 inches (1.30 m), with the tail surfaces being enlarged and their shape modified.

[3] The P-2J was phased out in the 1980s in favor of the P-3C Orion,[3] which eventually replaced the Neptune in the ocean-patrol air fleets of the West.