It is believed that in 1240 A.D.; (approx). The first King of Ahom reign Chow Chukafa established his capital at a place named Haboong in the district of Dhemaji. Due to perennial flood in the area the King shifted the capital from Haboong and after that the area became under the rule of Chutias and it continued from 1223 to 1523 A.D. During 1523 A.D. the then Ahom King Chuhung - Moong attacked and kill the Chutia king Natipal and as a result the area again became under the kingdom of Ahoms.
The entire Dhemaji district area was originally inhabitated by various indigeneous tribes like Mising, Sonowal Kachari, Bodo Kachari, Deori and Laloong. In addition to this different tribes e.g. Ahom, Rabha, Tai - Khamti, Konch, Keot, Koiborta, Brahman, Kayastha, Kalita etc. were migrated during different moments of time span.
There are a number of mythological and hypothetical believes regarding the origin of the name "Dhemaji". One of the most popular believe is that - there was a river which used to change its course very frequently and resulted unanticipated flood covering different parts of the area. Hence the river was believed to be a kind of evil spirit. The Assamese version of the words flood and playing are "Dhal" and "Dhemali" respectively and therefore the area when flood is a perennial phenomenon may be called as a playground for flood i.e., in Assamese it became to be "Dhal Dhemali" with the ellapsation of time the word "Dhal" was omitted and also the word "Dhemali" started to be pronounced as "Dhemaji".
Initially, the present geographical area of Dhemaji district was a part of the then Lakhimpur District with its headquarter at Dibrugarh. In 1971 Dhemaji was declared as a Sub-Division, Including Jonai and Dhakuakhana (Presently under Lakhimpur District) 14th Aug/1st Oct, 1989 Dhemaji was declared as an independent district covering Jonai and Dhemaji (Sadar) Sub-Divisions.