He told the court his ex took the boys to an emergency room in March without letting him know they wouldn't make it to Miami for a scheduled visit. He was questioned by a lawyer representing his children.
During a break, Wade expressed some relief that he's getting to tell his side to the court. He said, "I mean, the best thing about testifying, period, is that you get the opportunity to let your voice be heard. Um, there's been a lot of things said throughout the litigation of this process, and I get an opportunity to finally say my side of things."
The attorney representing Wade's ex-wife tried to establish that she is the primary parent who has cared for the children every day.
While Wade was in Chicago, his team practiced in Miami.
"What he's dealing with is way bigger than basketball," Heat forward LeBron James said. "So when he's ready to come back, when he's ready to return, we'll accept him with open arms, of course. We'll make sure we hold it down here. What he has going on, we're all in support, this whole organization, us as teammates, us as friends, us as a family."
It isn't clear how long Wade will be in town. The custody case has been going on for weeks, and the battle with Wade's now-ex-wife Siohvaughn Wade has been waged for considerably longer.
On his Twitter feed Sunday, Wade indicated that he would not be back in time to see Miami host Charlotte in a preseason game Monday night. His schedule for the rest of the week seems in doubt as well, although there has been no indication that Wade won't be ready -- physically or emotionally -- for the Oct. 26 regular-season opener in Boston.
"Hopefully," Heat coach Erik Spoelstra said, "if there's no setback."
Wade had hoped of getting in at least one of Miami's final two preseason games, in Atlanta on Thursday or against Orlando at Tampa, Fla., on Friday. His status for those contests would seem, at best, doubtful.
Wade's absence didn't dampen the mood Sunday, an event primarily for season-ticket holders. Miami has already played two home preseason games, so plenty of South Florida fans have gotten a chance to see James, Chris Bosh and the rest of the revamped roster.
Didn't matter. A 12-minute scrimmage Sunday was received like a playoff game.
"It has been electric," Spoelstra said. "We want to do our part, and that's coming in every single day, working and trying to build this team. But it's great to see the support and the fact that the fans are ready."
Fans were greeted by Alonzo Mourning, who was cheered at first, then playfully booed when he said he wasn't coming out of retirement. Heat president Pat Riley spoke before the workout as well, his words often getting drowned out by the reaction of the crowd.
"We are extremely appreciative of your support and we hope that you're going to have one truly exciting year," Riley said. "And I think you will enjoy this whole process."
What certainly isn't enjoyable for the Heat to watch is Wade's legal process.
Wade originally hoped the custody case would be done before training camp opened last month, but as with just about everything involving his divorce and the subsequent legal fallout, delays have popped up often along the way.
So while he's trying to get his leg right -- Wade was hurt three minutes into the preseason opener -- his family issues are taking priority, with his team's blessing.
"You understand that situation, that comes before anything," James said. "Any time you're dealing with family, that comes before anything, and whenever he returns, then we'll be ready."
Notes: James showed no ill effects from his right hamstring cramp issue that popped up last week, and since he went through practices Saturday and Sunday without problems, he's expected to be available for Monday night's game. ... Heat guard Mario Chalmers is still day-to-day with his sore left ankle, though has been working out, Spoelstra said. ... Without Wade, the Heat had a first team of James, Carlos Arroyo, Mike Miller, Joel Anthony and Bosh for the open scrimmage.
The Associated Press contributed to this report