Born on June 6, 1967, Sahoo belongs to Daspalla in Nayagarh district and is the son of Dandadhar Sahoo. He completed his M.A. from Utkal University, Bhubaneswar in 1990 and later obtained his LL.B. degree from Vani Vihar Law College in 1993. In 2013, he completed his Ph.D. in History from North Odisha University, Baripada.
Arun Kumar Sahoo first became MLA in 2004 and has consecutively won the Odisha Legislative Assembly elections in 2004, 2009, 2014, 2019, and 2024 from Nayagarh constituency. In the 2024 Odisha Assembly Election, he secured 81,959 votes and defeated BJP candidate Pratyusha Rajeshwari Singh by a margin of 439 votes.
He is widely known for his active role in Odisha politics and his long association with the Biju Janata Dal under the leadership of Naveen Patnaik.