Two others arrested with them in late May were acquitted. All were accused of forming an illegal cell and financing a terrorist organization. The defendants admitting transferring $400,000 to Islamic State, senior Kuwaiti sources said.
The United States and other Western countries have criticized Kuwait for what they have described as a permissive approach to militant financing. Open fund-raising events have been held in Kuwait for jihadist causes in Syria and Iraq.
The defendants said the people who had collected donations from Kuwaiti tribes in 2012 were not aware of where the money was going and that it had been solicited under the pretext of providing humanitarian supplies to refugees, the sources said.
The money was delivered to Islamic State through intermediaries in Aleppo and Deir al-Zour in Syria, after passing through the United Arab Emirates, Jordan or Turkey, the sources said.
Islamic State raises most of its revenues by taxing people, businesses and trade in areas it controls, but it also gets money from wealthy donors, principally in Gulf countries.