In 1964, Opel introduced the completely new KAD (Kapitän, Admiral, Diplomat) models; the Kapitän served as the base model of this three-tier model range.

It was powered by the same engines as the contemporary Opel Admiral, namely a 2.6-L-inline six or a 2.8-L-six; a few Kapitäns even received the Chevrolet-sourced 4.6-liter V8. For the Austrian market, 580 Kapitän and Admiral models received the 2.5-liter version of the CIH six with an output of 112 PS (82 kW; 110 hp) in 1966 and 1967.

Like its more expensive brethren, the Kapitän was reworked in late 1967 and received rub strips, a new ZF steering and a collapsible steering column. At the same time, a new HL (Hochleistung = high-performance) version of the 2.8-liter six became available that put out 140 PS (103 kW; 138 hp).

Sales of the Kapitän A fell sharply off; up to its discontinuation in November 1968, a total of 24,249 cars left the factory.