The baby girl, who weighed 8 lbs., 1 oz., and was 21 1/2 inches long, was born at 4:57 a.m. (EST) in Miami.
O'Neal, 34, made it back from Chicago, where his team, the Miami Heat, were playing the Chicago Bulls, in time for the birth.
"My wife, Shaunie, and I had another beautiful baby girl, Me'arah Sanaa." O'Neal said in a statement. "Each child that we have adds another lifetime of joy to our lives. Family is extremely important to me, so I was overcome with extreme happiness when Me'arah arrived healthy and beautiful."
The couple already have three children together, sons Shareef, 6, and Shaqir, 3, and daughter Amirah, 4. O'Neal has a daughter Taahirah, 9, and Nelson has a son Myles, 8, from previous relationships.
"What most people don't know about (O'Neal) is what a great dad he is," Mindy Weiss, the party-planner who organized a recent baby shower for the couple, told PEOPLE in March. "He loves having lots of children, and I think he'd like to have more. But they've decided this is their last one, since they now will have six children."
The basketball great and Shaunie, 31, wed in 2002, in a private ceremony before 248 guests at the Beverly Hills Hotel.