Robert Scott, 36, had been due to go on trial for the murder of Richard Hicking at Belfast Crown Court - but defence QC Arthur Harvey asked for the charge to be put again.
When it was, Scott, from Clarawood Park, simply said "guilty".
The body of 31-year-old Mr Hicking was found in his flat, also in Clarawood Park, around 12.30pm on Saturday, 30 April 2011.
Multiple stab wounds caused his death.
Following the guilty plea on Tuesday, Mr Justice McCloskey told Scott that under law, "as a matter of obligation I must now perform the duty of sentencing you to life imprisonment".
He explained to Scott that once probation pre-sentence reports and any other reports had been compiled, he would then fix the minimum period he must spend behind bars, but added "your release from prison will not be a matter for this court".
"That will rather be a matter for a different judicial body, the Parole Commissioners...they will decide whether it is essential for the protection of the public for you to be detained," said the judge.
Remanding Scott back into custody, Mr Justice McCloskey adjourned the case until 8 February.