Darren Joseph Casey, whose address was given as Claragh Hill Grange, Kilrea, pleaded guilty to the offence at Antrim Crown Court, last week.
He is due to be sentenced at Laganside Courts on Friday, September 5, 2014.
Mr McKeown, who was 21 at the time, entered the River Bann at the Bann Road Bridge on Saturday, May 5, 2012. His body was found the following day.
A number of people were arrested as part of the investigation into his death.