O'Brien has hosted two Winter Olympics, the Superbowl, the World Series, the NBA Finals, the NBA All Star game, the NCAA Final Four tournament, Baseball's All Star game, the US Open Tennis Championship, college football's national championship game, the World Figure Skating Championship, and other premier sporting events.

Pat O'Brien's broadcast career began in 1970 when, after graduation from the University of South Dakota, he was hired as a researcher at NBC News in Washington , D.C. O'Brien later worked at WMAQ-TV Chicago as a reporter. In 1977, he moved to KNXT (now KCBS-TV), the CBS owned television station in Los Angeles, as a reporter. While there, O'Brien earned four local Emmy Awards for his news coverage. Pat O'Brien also received a Los Angeles Press Club Award in 1987 for news writing.