The Central Bureau of Investigation arrested poetess Madhumita Shukla's 'killer' in Lucknow on Monday morning.
Prakash Chander Pandey will be produced in court later in the day, CBI sources said.
The sources said Pandey was arrested following interrogation of his accomplice Santosh Kumar Rai alias Satya Prakash.
The duo had visited the Lucknow residence of the 24-year-old poetess and shot her dead, they said.
The CBI has already arrested former Uttar Pradesh minister Amarmani Tripathi in connection with the murder.