The 1978 Cologne Cup, also known as the Cologne Grand Prix, was a men's tennis tournament played on indoor carpet courts in Cologne, West Germany that was part of the 1978 Colgate-Palmolive Grand Prix circuit.

It was the third edition of the tournament and was held from 30 October through 5 November 1978.

Fourth-seeded Wojciech Fibak won the singles title and the accompanying $10,000 first-prize money Wojciech Fibak defeated Vijay Amritraj 6–2, 0-1, ret.

Peter Fleming / John McEnroe defeated Bob Hewitt / Frew McMillan 6–3, 6–2