Marino had one goal and 24 assists in 81 games this past season.
The 25-year-old from North Easton, Mass., has registered 10 goals and 54 assists in 189 games during his three years with Pittsburgh.
He was drafted in the sixth round, 154th overall, by Edmonton in 2015 but never played with the Oilers and was dealt to the Penguins in 2019 after finishing his third year at Harvard University.
"John is a competitive, highly mobile defenceman who strengthens our back end," Devils general manager Tom Fitzgerald said. "He takes pride in his game away from the puck and his puck management and ability to transition play will fit in nicely with our style and the strengths of our forward group.
"This is another move focused on improving our club today, while also providing certainty and stability for roster flexibility as we continue to build."
Smith, 22, had two goals and 21 assists during his rookie campaign in 2020-21 and followed that up with five goals and 15 assists this season.
Drafted 17th overall by the Devils in 2018, the Lloydminster, Alta., native earned a gold medal with Canada at the 2020 world junior championship.