Keya Morgan was taken into custody in Arizona on an outstanding arrest warrant after being charged by Los Angeles County prosecutors earlier this month.
Mr Morgan faces felony charges including theft, embezzlement, forgery or fraud against an elder adult, and false imprisonment of an elder adult. A misdemeanour count also alleges elder abuse.
Police say Mr Morgan pocketed more than $262,000 (£206,000) from autograph signing sessions Lee did in May 2018.
Authorities say Mr Morgan sought to capitalise on the Marvel Comic mastermind’s wealth and exert influence over Lee even though he had no authority to act on his behalf.
At one point Mr Morgan also took Lee from his Hollywood Hills home to a Beverly Hills condominium “where Morgan had more control over Lee”, they said.
Lee’s daughter said in a request for a restraining order last year that Mr Morgan was manipulating the mentally declining Lee, preventing him from seeing family and friends, and trying to take control of his money and business affairs.
Attorney Alex Kessel has said Mr Morgan has never abused or taken advantage of Lee.
Mr Kessel said on Saturday he had been in contact with prosecutors to arrange for Mr Morgan to surrender on Tuesday.
“It is unfortunate that the DA and police did not honour our commitment to surrender next week and arrested him,” Mr Kessel said.
Lee died in November at the age of 95.
Mr Morgan’s bail has been set at $300,000 (£240,000). He will eventually be sent to Los Angeles to face the charges.