A rep for Kingston tells us, "Sean is breathing on his own and walked for the first time this morning."
"Sean Kingston continues to be hospitalized at Jackson Memorial Hospital in Miami. His condition has been upgraded to serious."
As TMZ previously reported, the "Beautiful Girls" singer was critically injured in a jet ski accident last weekend -- and had been attached to a breathing tube. So today's news in VERY GOOD.
Kingston's rep adds, "Sean thanks his friends, family and fans for their outpouring of prayers and well wishes.”