The 83-year-old crown prince was proclaimed the new emir by Kuwait's council of ministers, according to the statement read on air.
Earlier in the day, Kuwaiti Minister of State for Cabinet Affairs Mohammad Abdullah Al-Mubarak Al-Sabah said Emir Nawaf Al-Ahmad Al-Jaber Al-Sabah died at the age of 86 on Saturday.
Russian President Vladimir Putin expressed his condolences to the new Kuwaiti emir on the death of his brother, the Kremlin said.
"Emir Nawaf Al-Ahmed rightfully enjoyed great authority in the Middle East. He did a lot for the socio-economic development of Kuwait and the strengthening of its position in the international arena. We appreciate his personal contribution to strengthening friendly Russian-Kuwaiti relations," the statement read.