According to the Ceylon chronicles he was placed on the throne by the people rebelling against the previous kings. He was the King’s Amatya or Minister. But he had gained respect under the weak successors of Ajatsatru and probably became the ruler in 413 BC. he proved to be a capable ruler and extended the territories of Magadha. The neighbouring rival state of Avanti, Vatsa and Kosala were defeated by him and their territories annexed to Magadha. He ruled for 18 years.
Sishunaga was succeeded by his son Kalasoka in 395 BC. He transferred his capital from Vaishali to Patliputra. The second Buddhist General Council was held during his time at Vaishali. He ruled for 28 years. According to the Buddhist literature Mahavamsa the 10 sons of Kalasoka ruled one after the other for 22 years. The Shishunaga dynasty came to an end in 344 BC.