The 26-year-old recently moved to Vale Park on a one-year deal following his release by Rotherham United.
While Port Vale finished 13 points adrift of the playoff places in the League One table last term, O'Connor believes that they are capable of challenging for promotion this time around.
"I'm happy to sign for Port Vale," he told the club's official website. "I've had three weeks where I didn't know what I was doing but the gaffer rang me last week and told me he wanted to sign me and I jumped at the chance to sign because this club has the potential to do big things."
Port Vale begin the new season at home to Walsall on August 9.