The person spoke on the condition of anonymity because the deal isn't expected to be announced until Thursday.
The person said on Wednesday night that team president Ed Stefanski will stay on as general manager. Stefanski had held both roles since he replaced Billy King in December 2007.
King replaced Thorn as New Jersey's, GM last month.
The hiring was first reported by Yahoo! Sports.
Thorn was president and general manager of the Nets for 10 years before leaving in early July. Thorn and Stefanski worked together in New Jersey and helped lead the franchise to consecutive trips to the NBA finals. The Nets lost both times.
He had called the shots for the Nets since 2000 and hired Avery Johnson as coach before resigning. Thorn helped turn the Nets into a contender in 2001 when he engineered a trade to bring Jason Kidd to New Jersey.
Before joining the Nets, Thorn was the NBA's executive vice president of basketball operations from 1986-2000.
This is the latest big move this summer for the Sixers after they missed the playoffs last year. They fired coach Eddie Jordan after one season and replaced him with Doug Collins. Then they traded disgruntled center Sam Dalembert and drafted Ohio State guard Evan Turner with the No. 2 overall pick.
Stefanski said after the season the Sixers took an "unacceptable" step backward in finishing 27-55 and missing the playoffs for the first time in three seasons.
Stefanski's job was never really guaranteed by ownership and now he has one less role to worry about.