Completion of the acquisition was announced Friday but no details were provided on financial details of the transaction.
PKMJ Technical Services is a nuclear engineering services business with headquarters in Pennsylvania.
"We are delighted with today's acquisition, which provides us with an excellent platform from which to grow the comprehensive plant optimization service that we already provide to our customers," said PKMJ President Paul Tobin. "Rolls-Royce is trusted to deliver excellence and we are proud to be a part of it."
Rolls-Royce said its nuclear services business involves solutions for managing nuclear power plants and extending their service life.
"Our investment in PKMJ represents another significant step toward growing our global civil nuclear business and providing customers with a suite of services to deliver safe and efficient lifecycle operations," Rolls-Royce-Nuclear President Lawrie Haynes said.
"PKMJ supports every nuclear utility in the U.S. and Canada with an impressive portfolio of services and solutions and employs some of the most highly skilled people in the industry. We look forward to welcoming them into our business."