Prior to serving in the Senate, O'Mara represented the 137th district of the New York State Assembly from 2005 to 2010.

He and his wife Marilyn have three children Thomas, Catherine and Caroline and reside in Big Flats, New York.

[5] In 2010, O'Mara was first elected to represent the 53rd District in the New York State Senate after surviving a strong primary challenge from fellow Assemblyman James Bacalles.

He defeated Democrat Pamela Mackesey in the general election and took office in January 2011.

[6] Since his initial election in 2010, O'Mara has never faced a serious re-election, running unopposed in 2012 and 2014.