Poom played as a goalkeeper for Lõvid, Sport Tallinn, KuPS, Flora, Wil, Portsmouth, Derby County, Sunderland, Arsenal, and Watford. Poom made his international debut on 3 June 1992 in Estonia's first official match since restoration of independence, a 1–1 draw against Slovenia in a friendly. He made a total of 120 appearances for Estonia and was the team's captain. Poom won the Estonian Footballer of the Year award six times, in 1993, 1994, 1997, 1998, 2000 and 2003, the second most times won, behind only Ragnar Klavan. In November 2003, Poom was named Estonia's Golden Player. He ended his career on 10 June 2009, after a 0–0 draw against Portugal.