Late singer Jackson's 14-year-old daughter Paris — who had been broadcasting her fears about her grandmother's whereabouts on Twitter for days — tweeted “grandma's here! #thankyougod” in the early morning hours.
Katherine Jackson was granted custody of Paris, Prince Michael, 15, and Blanket, 10 after their father's death.
But judge Mitchell Beckloff suspended that arrangement on Wednesday because the Jackson family matriarch had left the family home in Los Angeles.
She later vowed to fight to regain legal guardianship of the children.
“I am devastated that while I've been away, my grandchildren have been taken away from me, and I'm coming home to see about that,” the grandmother said in an interview with ABC News.
The fractious family has been embroiled in legal and financial disputes since the pop star's sudden death in June 2009 from an overdose of Propofol, a powerful anesthetic.
Entertainment media portrayed the 82-year-old Jackson's absence as an abduction by Michael's siblings, who are allegedly furious they did not inherit any of the singer's assets.
Paris fueled the speculation with a series of tweets in which she insisted her grandmother was “missing” and wrote “something is really off, this isn't like her at all ... I wanna talk directly to my grandmother.”
But Katherine Jackson insisted she was visiting a spa in Arizona to rest and that rumors of a kidnapping were false, telling ABC News “My children would never do anything to me like that.” Prince Michael was not convinced.
“As long as I can remember my dad had repeatedly warned me of certain people and their ways,” he wrote in a lengthy tweet.
“Although I am happy my grandma was returned, after speaking with her I realized how misguided and how badly she was lied to. I'm really angry and hurt.”
Prince Michael also lashed out at his relatives for denying the children contact with their grandmother while she was in Arizona.
He published a screenshot from a group text message chat in which Janet Jackson apparently wrote “Don't let them pls” after he wrote “This is enough so I am texting you for the simple fact that WE DEMAND TO SPEAK TO MY GRANDMA NOW!!!”
Katherine Jackson condemned the “bunch of lies” that led to the public dispute and her loss of guardianship, saying: “I have a good idea who's doing that and who's behind that.” Jackson said the reason she didn't call her grandchildren for more than a week was because “I just gave up my phone and I didn't want to have any phone calls while I was here.” Her lawyer Perry Sanders said his client was at the Miraval Arizona Resort & Spa in the city of Tucson “because of her high blood pressure and to get some R&R (rest and recuperation).”
Jackson explained that she had made arrangements for TJ and the household staff to watch the children in her absence, but that someone intervened and told the cook, the nanny and the housekeepers to go.
“I don't know who did that but they don't have that power and they shouldn't have done it,” Jackson told ABC.