In October 2004, Kassar was appointed minister of economy and trade in the cabinet led by prime minister Omar Karami, replacing Marwan Hamadeh as economy minister. His tenure lasted until the year 2005, when Karami resigned from office due to the pressures exerted by Lebanese people as a protest over the assassination of Rafik Hariri. Kassar was succeeded by Demianos Khattah in the post. Later Kassar served as the minister of state in the cabinet led by prime minister Saad Hariri from November 2009 to 2011. Kassar was one of the cabinet members appointed by the Lebanese president Michel Suleiman.