He was first elected in 2002 on the Industrial and Commercial Panel and was appointed Seanad spokesperson on Communications, Marine and Natural Resources. He was re-elected in 2007.
Before the 2011 general election MacSharry was appointed to the Fianna Fáil front bench on 31 January by the new leader Micheál Martin. He was appointed as spokesperson on Tourism and Arts. MacSharry was a candidate at the 2011 general election in the Sligo–North Leitrim constituency but was not elected. He was re-elected to the Seanad in April 2011 and was appointed Fianna Fáil Seanad spokesperson on Health.