Each of the five rounds were incredibly well contested by both, but Edwards was adjudged to have landed the cleaner shots.
The Jamaican-born fighter was keen to avoid expending too much energy and opted to attack with strong kicks at a distance.
Usman's tactics changed throughout the fight as he attempted to ground his opponent numerous times.
Edwards had a clear speed advantage over the Nigerian, able to recover quickly and cause problems.
Judges scored it 48-46, 48-46, 47-47 to give 'Rocky' a majority decision.
"I couldn't get the kick around his head," said Edwards after the fight on BT Sport. "He had the perfect defence, I was trying to set it up with kicks to the body and legs.
"I know it was a close fight, so I knew I had to land the cleaner shots. He didn't land many clean on me. He just had lots of pressure."