They also agreed to deals with three other players, left wings Doug Doull and Pat Leahy, who also signed one-year contracts, and center Robert Liscak, who got a two-year deal.
Financial terms were not disclosed.
Moran, 30, the key signee, was acquired from Pittsburgh for a 2004 fourth-round pick at the March 11 trade deadline, when Boston also acquired fellow defenseman Dan McGillis from San Jose.
"We were happy with what Ian brought to the team when we acquired him in March, and we maintained at the end of the season that we'd like him to return," said General Manager Mike O'Connell. "He is a very steady defenseman and is another veteran presence in the dressing room."
Moran, a native of Acton, had spent his entire career with the Penguins. In 441 games, he had 19 goals, 45 assists, and 283 penalty minutes.