Four young men on trial for gang raping a teenage girl at a NSW house party have been found not guilty.

A jury on Wednesday found Christian Dickens, 22, Aaron Jensen, 23, and two 21-year-old men not guilty of aggravated sexual assault in company at a Blue Mountains house in 2012 where a 15-year-old girl alleged she'd been attacked.

Judge Leonie Flannery discharged the jury at Sydney's Downing Centre District Court as the accused men's families applauded the verdicts.

The four co-accused smiled and hugged family members as they walked out of the dock.

Outside court, Dickens said he felt relieved.

"Not guilty's great," he said.

He said it was "heartbreaking" when the jury delivered its verdicts, almost seven weeks after the Crown opened its case.

AAP