"We had an extensive discussion about the issue of human rights, right through to the discussion of religious plurality," he told reporters after talks with his Saudi counterpart Prince Saud al-Faisal.
"The government of the Kingdom of Saudi Arabia is aware that the European Union has a clear position on the issue of the death penalty: we are convinced that the death penalty should be abolished around the world."
Prince Saud told the same news conference that during their discussion, he had made clear to Westerwelle that regional, cultural and religious traditions must be respected.
"I would like to stress that we talked about human rights and that includes different criteria between countries," Saud said. "We reached the conclusion that these matters cannot be imposed by either side summarily and a change cannot come unless is it by conviction."
Human rights activists in Germany had called on Westerwelle to take up the issue of gay rights during his one-day visit to Saudi Arabia, where Islamic sharia law permits the imposition of the death penalty for a range of "crimes" including homosexual relations.
Sources who took part in the talks said Westerwelle directly addressed the issue of human rights and the death penalty in his talks with Prince Saud, and asked about the work of the government-created Saudi Human Rights Commission.
Prince Saud described the efforts of a so-called national dialogue taking place between traditionalists and modernisers, as well as Sunni and Shiite clerics, the sources said.
Westerwelle, who arrived in Riyadh late Friday with a business delegation, also held talks with the country's finance minister. He was also due to meet King Abdullah before flying to Qatar for talks on Sunday.