The WBC belt holder was defending his title for the fifth time and added the IBF and WBO belts with what he described as a 'comfortable' win over Kamboso of Australia in front of 41,129 fans at Marvel Stadium in Melbourne.
"This is a dream come true," he told reporters.
All three judges scored the bout in the 23-year-old American's favour, 116-112, 116-112 and 118-110, as home fancy Kamboso suffered a first professional defeat in 21 bouts since his debut in 2013.
"I was comfortable. I was sticking to the gameplan. The gameplan was to go in and hit and not get hit, and I did that for the majority of the fight," said Haney.
"I took the last round off because I knew I was comfortably ahead, but I fought a good, smart fight."
'The Dream' ultimately proved too elusive when extending his professional record to 28-0 (15 KOs) and becomes the first undisputed lightweight champion since the late Pernell Whitaker in 1990.
Kambosos, who became world champion with victory over Teofimo Lopez at Madison Square Garden in New York City in November 2021, immediately outlined his hopes for a rematch with Haney.
"I want to take the best test, the hardest test and I'm going to give him full respect for his victory and let him have his time," said the Australian.
"We'll do it again. I have to implement a few things but I thought the fight was very close."