Okonkwo has penned a three-year deal with Wrexham, having spent last season on-loan with the Welsh club.
"I’m feeling very good, I’m so happy to have finally signed and I can’t wait to get back to it," said Okonkwo.
"It was amazing last season. We had so many good memories together with the fans, and knowing they wanted me back was a big reason that I’m back. It’s good to finally be here.
"This is home, it’s felt like that since last season when I came in. The co-chairmen are so good, the manager, the coaches, the players, and obviously the backroom staff that you don’t see. It’s so good to be here."
Wrexham manager Phil Parkinson said: “We’re delighted with the signing. It’s such an important one for us.
“Arthur was outstanding for us last year, and since the season finished we’ve worked really hard to secure the signing."