Brunei Darussalam joined the IsDB on 3rd April 1986. Its subscribed capital is ID128.4 million (0.28% of total IsDB subscribed capital). The first operation was approved in 2000. The last project was approved in 2015 by ICD.

Brunei Darussalam is a small Sultanate on the northwest coast of the Island of Borneo. It occupies 5,765 square kilometers and is divided into two parts, both of which are surrounded by the Malaysian state of Sarawak. The population of Brunei is estimated at 0.4 million (2017). Brunei's official language is Malay, but English is widely understood and used in business. His Majesty, the Sultan is the supreme executive authority in Brunei Darussalam. Bruneian officials, including the Sultan, regularly meet with their regional counterparts in Association of South-East Asian Nations (ASEAN).