Isuzu has used both its own engines and General Motors-built engines. It has also developed engines for General Motors, Renault, Saab, Honda, Nissan, Opel and Mazda.

Isuzu engines carry a two-character prefix which designate the number of cylinders and engine family. Engines available currently include the following:

Isuzu's first petrol engines were license built Hillman units for the locally assembled Minx, from 1953. Called the GH10 it has a bore of 65 mm (2.56 in) and a stroke of 95 mm (3.74 in) for a displacement of 1,260 cc (76.9 cu in). Power is 37.5 PS (28 kW). In 1955 this was updated to the GH12, a square design with a 76.2 mm bore and stroke for a displacement of 1,390 cc (84.8 cu in). This was upgraded in 1956 for more power, 46 PS (34 kW) rather than the original's 43 PS (32 kW), and was renamed GH100. In 1958, power increased yet again, to 50 PS (37 kW).

For 1959 Isuzu developed their own square design (78 mm or 3.07 in) called the GL150, Isuzu's first own petrol engine. Still showing unmistakable Hillman origins it displaces 1,491 cc (91.0 cu in) and has 60 PS (44 kW). The GL150 was fitted to the 1959 Isuzu Elf and the 1961 Bellel.

Isuzu considered the B engine their "small" truck engine. Initially designed in 1969 as a 3.6-liter four cylinder or a 5.4-liter six-cylinder direct injection unit, other displacements were added later on. In 1980 a 3.3-liter version appeared.

Isuzu's C-series engine was a mainstay for their light truck production, as well as for industrial and marine uses. The engine was introduced in 1959; by 1985 over 2 million units had been produced. It was replaced in 1985 by the larger J-series engine.

This family of engines started as the swirl chamber design, later modified into direct injection (4EE1), with a final improvement into a 16-valve direct common rail injection (4EE2).

All engines are SOHC with direct injection and are normally aspirated (N/A) or turbocharged (T) or turbocharged and intercooled (T/I)