The wooden motor boat was heading from the east of the main island of Java to Bali yesterday when its engine failed, Supriyono, search and rescue chief in the city of Surabaya, told AFP.
The captain managed to briefly call authorities soon after the boat broke down, and reported about 20 people were on board, said the official, who like many Indonesians goes by one name.
However the official added that authorities had not been able to get in touch with the skipper since, and the vessel's location was unclear.
Indonesian news agency Antara reported that family members of the bride and groom were believed to be on the boat, but it was unclear whether the couple themselves were.
Indonesia relies heavily on boats to connect its more than 17,000 islands, but has a poor maritime safety record.