After attending Colorado College for three years, Greg Smith joined the team that selected him in the 1975 Amateur Draft for the 1975-76 season, the California Golden Seals, with a one game debut. When the team moved to Cleveland where they became the Barons, Smith followed and spent two seasons with them.
Smith was protected by the Minnesota North Stars in the 1978 Dispersal Draft and saw his first Stanley Cup playoff action in 1980 as the team made it to the semi-finals. The 1980-81 season saw Smith and Minnesota make a run for the Cup as they cruised through the playoffs until meeting the Islanders in the finals. Although many fans cheered for the underdog North Stars, they proved no match for the powerful Islanders who won their second straight Cup on the way to four in a row.
In 1981, Smith was dealt to the Red Wings where he played for eight years before being traded to the Capitals in 1986. Smith ended his playing career in 1988 after three years in Washington.