The Six Million Dollar Man actor is expected to appear in at least two instalments of the TNT series' second season as Ken Richards, reports Entertainment Weekly.
[Left: Lee Majors / Right: Patrick Duffy in 'Dallas']
Ken Richards is described as a former love of Sue Ellen Ewing (Linda Gray) who meets up with her again over a business matter.
Dallas's second season will also feature the returns of original series favourites Deborah Shelton, Cathy Podewell, Ted Shackelford, Steve Kanaly and Charlene Tilton as part of the show's send-off to the late Larry Hagman, who played JR Ewing.
Patrick Duffy recently revealed that Dallas's tribute to Hagman will remain in the spirit of the series.
"We'll be dealing with the situation [of Larry's passing] in a really artistically sensitive, correct way," Duffy said earlier this month.
Dallas airs on TNT on Monday nights and on Channel 5 in the UK the following day.