They displayed a Croatian flag on the world's highest peak at 0940 hrs local time in Nepal.
Darija and Iris Bostjancic are the first sisters to scale this height together.
The Bostjancic sisters and Vedrana Simicevic conquered the world's sixth highest peak, Cho Oyu, on 2 October 2007.
Cho Oyu is 8,201 metres high, and the three alpinists were the first Croatian women to scale a height of over 8,000 metres. It was the first time two sisters stood on this peak at the same time.
The sisters Bostjancic and Simicevic were members of the first all-female Croatian climbing team. Cho Oyu, whose name in Tibetan means "turquoise goddess", is situated in the Himalayas on the border between Tibet and Nepal, about 35 kilometres west of Mount Everest.