Bradley Plavecz (20) of Arkwright Way, Gunthorpe had admitted stabbing Daniel Szalasny at the party in the early hours of May 8 last year, but denied murder.
But after a week long trial at Peterborough Crown Court, he was found guilty by a jury.
The court had heard how Plavecz suffers from ADHD, and it had been argued by his legal team that the disorder meant he had been unable to exercise self control, meaning a manslaughter verdict would have been open to the jury.
However, the prosecution said this was not the case, and the ADHD did not substantially affect his ability to exercise self control.
The 11 jurors - one juror was forced to drop out of the case part way through the trial - returned their guilty verdict this afternoon.
The court had heard how Plavecz and Mr Szalasny had never met before the night of the party in Crown Street - but the pair had argued on the night.
CCTV footage captured the stabbing, and the moments leading up to the fatal incident. A few seconds before he was killed, Mr Szalasny had punched Plavecz to the face,
Plavecz said he had picked up a kitchen knife from the sink at the party, and concealed it in the waistband of his trousers. He said he then ‘blanked out’ and could not remember the stabbing itself.
Mr Szalasny died at the scene.
Plavecz will be sentenced on Thursday, January 27- but he faces a mandatory life sentence.