The harbour for Irvine has a long history and once was one of the most prominent ports in Scotland after Glasgow. Across from the main harbour itself there was a terminal for the ICI-Nobel Explosives plant on the River Garnock. Much of the harbour went into decline in the 19th century when Glasgow, Greenock and Port Glasgow achieved higher prominence as sea ports. Despite this, there was still commercial sea traffic, though the harbour went into further decline in the 20th century. The main shipping in the 20th century was light coastal traffic and vessels destined for the Nobel Explosives facility. This facility had its own quay, which, although now disused, is still visible from Irvine Harbour. A shipyard on the River Irvine, the Ayrshire Dockyard Company, remained active until after World War II, though its last ship was built just prior to the war.

Afterwards it was involved in refitting ships and also in the manufacture of fittings for other vessels including the Cunard liner Queen Elizabeth 2. Irvine Harbour is now officially closed as a commercial port and houses a small number of privately owned pleasure craft. It is also home to part of the Scottish Maritime Museum with numerous vessels on display, including the 'Spartan', one of the last surviving Clyde puffers.