Machhendra Nath alias Baba Pratibhanand, who carried a bounty of Rs 1 lakh by the Delhi Police, was on the run for the last four years, police said.
On Friday around 10 pm a team led by Superintendent of Police (City) Akash Tomar arrested Pratibhanand, police officer SK Saxena said.
Pratibhanand is a resident of Beed in Maharashtra.
Mr Bhardwaj, who had contested the Lok Sabha election on a BSP ticket in 2009, was the richest candidate in Delhi, having declared assets worth Rs 600 crore.
He was shot dead at his 34-acre Nitesh Kunj farmhouse near the toll plaza in Gurgaon on March 26, 2013. Two or three criminals on a motorbike had shot Mr Bhardwaj dead, Delhi Police said.