Rodman is expected to land at Pyongyang's Sunan International Airport at 3:35 PM local time (4:05 PM KST).
Rodman spoke briefly to reporters before his flight from Beijing to Pyongyang.
"Anyone who knows Dennis knows he's trying to use his relationship to open the line of communication and send a message of peace and understanding", Prince said.
North Korea has very poor medical care and his exact medical condition is not known.
Rodman with Mr Jong-Un in 2014.
Nicknamed "the Worm", Rodman won two championships with the Detroit Pistons and three with the Chicago Bulls.
Adding another chapter to Dennis Rodman's peculiar relationship with North Korean leader Kim Jong Un, the former National Basketball Association star is expected to arrive today for his first visit since Donald Trump took presidential office, according to the Associated Press. North Korea's Supreme Leader is reported to be a major basketball fan.
His entourage included Joseph Terwilliger, a professor who has accompanied Rodman on previous trips to North Korea. Rodman said that issue is "not my objective right now".
Rodman also visited North Korea in January 2014, just weeks after Kim made a stunningly violent move to strengthen his grip on power - executing his uncle and onetime No. 2 Jang Song Thaek for alleged treason. The unlikely pair ended the evening with drinks and dining on sushi.
In the past, North Korea has held out until senior US officials or statesmen came to personally bail out detainees, all the way up to former President Bill Clinton, whose visit in 2009 secured the freedom of American journalists Euna Lee and Laura Ling.
Secretary of State Rex Tillerson confirmed the release, and said Washington remains in talks with the isolated regime "regarding three other USA citizens reported detained".
The North has occasionally jailed USA citizens and released them only after visits by high-profile political figures, including former president Bill Clinton. But in 2013, Trump praised Rodman's trips to North Korea, calling him "smart".
The announcement came amid tension between Washington and Pyongyang following a series of missile tests by the North, focusing attention on an arms buildup that Pentagon chief Jim Mattis on Monday dubbed "a clear and present danger to all".
North Korea has freed an American university student after holding him for 17 months, a move that could signal a conciliatory tone towards Washington amid intensifying US pressure on the regime over its nuclear and missile programs.
Warmbier was visiting North Korea as part of a tourist group arranged by Young Pioneer Tours, a tour agency based in Xian, China.
Before his trial, Mr Warmbier said he tried to steal the propaganda sign as a trophy for an acquaintance who wanted to hang it in her church.
North Korea has released American college student Otto Warmbier, who is on his way back to the US and won't be forced to serve a 15-year prison term, according to Secretary of State Rex Tillerson.
US Secretary of State Rex Tillerson denied that charge last month, saying the US is only seeking denuclearization, but the Trump White House has publicly abandoned the Obama-era strategy of strategic patience.