His mother, Wendy Mailey, confirmed the news to InsideCarolina.com on Friday afternoon.
Mailey told IC that her son's decision was made with the counsel of his immediate family. She also provided a quote from Hairston detailing his decision.
"I have spent a lot of time with my family over the past couple of days discussing school and my future, and I have finally decided today to return to the University of North Carolina for my junior year," Hairston said. "I value the experiences I have had over the past two years in Chapel Hill, and hope to continue to grow under Coach Roy's guidance. Coach always says ‘when you focus on the team during the season, he will support us in the offseason' - this is my way of supporting coach, my teammates and the Tar Heel community. Go Heels!"
Mailey also provided her thoughts on her son's decision to return.
"Throughout this process, it has been amazing to watch P.J. utilize the values we have taught him," she said. "I am proud that he took the initiative to weigh the impact of short-term gratification versus long-term success to come to his decision to stay in school. I've watched him continually mature and learn from each lesson he has been faced with over the past two years. And now, his commitment to furthering his education, and to his coach and teammates, further exemplify his growth."
Hairston increased his draft stock with a strong finish to the 2012-13 season. He started UNC's final 13 games at the 4-spot and averaged a team-high 18.2 points per game during that stretch.
ESPN.com projected Hairston as a late first-round draft pick earlier this week.
The Greensboro, N.C. native led UNC in scoring with 14.6 points per game last season and shot 39.6 percent from 3-point range. His 89 made 3-pointers are the second-most in school history, trailing only Shammond Williams (95 in '96-97). He scored 20 or more points in six of his 14 starts.