The wife of the rock 'n' roll icon welcomed the first visitors to the new attraction in Memphis, Tennessee on Thursday (02Mar17).
The complex, which sits across the street from his famous Graceland mansion, includes a 20,000-square-foot sound stage to host live performances and screenings of Elvis related films.
It also hosts exhibitions of artifacts from the Blue Suede Shoes singer's career and items of memorabilia from other artists who he inspired.
"This new exhibit and entertainment complex finally provides the right venue to make the Graceland visitor experience even greater,"Priscilla said at the grand opening. "Among many new exhibits, we are celebrating Memphis music history, which Elvis was always so proud of."
Thursday's inauguration of the new $45 million complex is part of a $140 million (£114 million) expansion of Graceland, a place of pilgrimage for fans of the rocker since his 1977 death from heart disease aged 42. Its opening follows the completion of a $90 million (£73 million) 450-room hotel last year (16).
Exhibits in the new complex include Elvis' extensive car and motorcycle collection, his famous stage costumes and personal items from his time in the U.S. Army.
In an interview with Memphis' News Channel 3, Priscilla, 71, also discussed her and Elvis' daughter Lisa Marie's contentious divorce from musician Michael Lockwood, which has seen her take custody of the couple's 8-year-old twin girls Finley and Harper.
"Like I said on my Facebook, I do have the children," she said. "They are doing great. They have never been in social services. I wanted to clear that up and we will see. We are sorting it all out and hopefully soon it will all be fine."
The children were removed from the family home by officials at California's Department of Children and Family Services (DCFS) after Lisa claimed to have found indecent photos and videos of children on her estranged husband Michael's computer.
In her Facebook post, Priscilla reassured fans that the children had not been taken into care, and she was looking after them while the allegations unearthed during divorce proceedings were investigated.
On Wednesday (01Mar17) Tennessee police announced they would not be investigating Michael, who denies the allegations.