Following his military service, he was named assistant at St. Paul Church in Cambridge in 1964, where he remained for three years before being named assistant at St. Mary Church in Waltham. In April 1970 he was named administrator of St. Christine Church in Marshfield, becoming pastor in July of that year. The St. Christine Parish history recalls that Father Sheehy's "gentle shepherding" avoided "much of the polarization experienced in other parishes" as the reforms of the Second Vatican Council were implemented.

After four years at St. Christine's, in February 1974, he was named pastor of St. Mary of the Annunciation in Danvers. In April 1980 he was named a member of the archdiocese's Pastor Evaluation Board and in October 1986 received his final assignment as parochial vicar at St. Francis of Assisi Church in Braintree. He served there until his retirement on July 1, 1991 and remained in the parish as a senior priest in-residence for many years. Remembrances by parishioners at St. Francis recall his faithfulness, cheerful demeanor and selfless generosity.

In 2006, Father Sheehy became a resident at the archdiocese's Regina Cleri residence for retired priests until earlier this year, when he moved to Marshfield to live with his niece Susan Farrell and her children Katherine A. Mulford and Charles W. Mulford, so they could assist him in his daily needs.

Father Sheehy's funeral Mass was held Aug. 22 at St. Francis of Assisi Church in Braintree followed by interment in North Weymouth Cemetery. The homilist was archdiocesan Secretary for Parish Life and Leadership Father Kevin Sepe, who had served as pastor of St. Francis of Assisi from 1998-2012. Designated concelebrants were Father Thomas W. Buckley, Father J. Michael Lawler, Father Darin Colarusso, Father Richard B. Martin of the Diocese of Arlington, Va., and Father Patrick Ryan, SJ.

He is survived by numerous nieces, nephews, grandnieces and grandnephews.