Smith played junior hockey for the Brockville Canadiens in 1959–60, making a Memorial Cup appearance in 1960. He began his professional ice hockey career with the Hull-Ottawa Canadiens of the EPHL from 1960 to 1963. He refused to report to the Springfield Indians in 1963 because he was wary of mistreatment by coach Eddie Shore. He played the 1963–64 season in Austria, under the assumed name Bobby Smith before joining the Indians, but only after being suspended by International Ice Hockey Federation President Bunny Ahearne for playing without his release. He played for the Indians from 1964 to 1967 and participated in the team's strike against Shore in 1966. Smith, along with teammate Bill White, got the little-known Alan Eagleson to represent the players in the conflict, which eventually started Eagleson's career as an agent. The players refused to practice and ultimately Shore was forced to sell the team to Kings owner Jack Kent Cooke for $900,000. When the NHL expanded in 1967, he was one of the players transferred to the new Los Angeles Kings franchise when they purchased the Indians franchise and its contracts, and he was one of the original Kings' players, playing the 1967–68 season with the Kings. He scored two goals against his brother, Gary Smith. In the following season, he played for the Phoenix Roadrunners of the Western Hockey League and the Memphis South Stars of the CHL. He then returned to the NHL with the Minnesota North Stars in 1968–69, and finished his career with the WHAHouston Aeros in 1972–73. He broke his jaw in an exhibition game and soon after his career ended. In 1973, Smith joined Ottawa television station CJOH-TV as the station's 6 p.m. sports anchor, a position he held until his death. He also participated in charitable activities, especially the Ottawa Boys and Girls Club.
Death
On August 1, 1995, Smith was shot in CJOH's parking lot, just minutes after the end of the station's 6 p.m. newscast. He was on his way to a charitable fund-raising event for the Children's Wish Foundation. He died about 18 hours later on August 2 in the Ottawa Civic Hospital. The gunman, Jeffrey Arenburg, was a paranoid schizophrenic who had gone to CJOH because he believed the station was broadcasting messages in his head. Smith was the first broadcast personality that Arenburg recognized coming out of the building. Smith's death was a shock to the Ottawa sports community. The Ottawa Senators honoured him with a 'Smitty 18' patch on their jerseys, which they wore for the 1995–96 season and with a banner hanging in the rafters at Canadian Tire Centre. The press box at Canadian Tire Centre was also renamed the "Brian 'Smitty' Smith Press Box" in his honour. Flags flew at half-mast at an Ottawa Lynxbaseball game, and a tribute was held by the Ottawa Rough Riders, whose players raised their helmets while the crowd joined in a one-minute cheer. Gunman Arenburg was found to be not criminally responsible due to his mental disorder and was sentenced to a mental institution in 1997. He had previously been sentenced to a mental institution but had never reported. An inquest into Smith's killing recommended there should be more public protection and significant changes to the Mental Health Act of Ontario. The end result, Brian's Law, was passed on June 21, 2000 by the Ontario Legislature. Smith's widow, Ottawa Citizen journalist Alana Kainz, established the Brian Smith Memorial Scholarship fund in Smith's memory, which provides tuition funds to attend college or university. It is administered by the Ottawa Boys and Girls Club. In 2001, the club renamed its summer camp from Camp Minwassin to Camp Smitty in Smith's honour. CJOH-TV established the Brian Smith Foundation to give disadvantaged children and young adults in the Ottawa region an opportunity to participate in athletics, recreation and education.