Ruutu started out playing for HIFK in the Finnish SM-liiga in the 1999–2000 season, and moved to Jokerit for the next two seasons.
In 2002, he returned to HIFK for one more season.
He was drafted by the Chicago Blackhawks in the 2001 NHL Entry Draft, as their first-round pick, ninth overall.
He then moved to North America in 2003, playing a full 82 games with the Blackhawks in the 2003–04 season.

Ruutu did not play during the 2004–05 NHL lockout, opting to take the time to recover from injuries, but provided commentary on Finnish television during the 2005 IIHF World Championship, along with fellow Finnish NHLer Ville Nieminen.
Ruutu returned to the NHL after the lockout but his 2005–06 season was cut short, first by a back injury that kept him out of the game for most of the fall, then by an ankle injury sustained in January that required season-ending surgery.

After an unimpressive showing at the 2006 IIHF World Championship, Ruutu contemplated retirement from playing professionally.
However, this notion was put to rest when Ruutu signed a two-year, $3.75 million contract extension with Chicago on 13 September.

During the 2007–08 season, on 26 February 2008, at the NHL trade deadline, the Blackhawks traded Ruutu to the Carolina Hurricanes in exchange for Andrew Ladd.
The Hurricanes promptly signed Ruutu to a one-year contract worth $2.25 million.

On 23 July 2009, the Hurricanes signed Ruutu to a three-year, $11.4 million contract extension, paying $3 million in 2009–10, $4 million in 2010–11 and $4.4 million in 2011–12.

On 22 February 2012, the Hurricanes signed Ruutu to a four-year contract extension worth $19 million.
The deal paid Ruutu $4 million in 2012–13 and $5 million per year in the remaining years; it also included a no-trade clause for the first three years of the contract.

Just hours before the end of the NHL trade deadline on 5 March 2014, Ruutu was traded to the New Jersey Devils in exchange for centre Andrei Loktionov.

In the 2015–16 season, Ruutu could not stay healthy and tallied one assist in the final game of the season.
Ruutu was not re-signed by the Devils once his contract expired, becoming an unrestricted free agent on 1 July 2016.
After going through the summer unsigned, Ruutu agreed to a professional tryout with the Vancouver Canucks on 13 September.

On 11 October 2016, Canucks general manager Jim Benning announced Ruutu had been released from his PTO contract.

On 28 October 2016, Ruutu was signed by HC Davos for the remainder of the season as a replacement for the injured Daniel Rahimi.
He made his NLA debut on 11 November 2016 and scored his first goal that same day in a 3–2 loss in Geneva against Genève-Servette HC.
Ruutu started out playing for HIFK in the Finnish SM-liiga in the 1999–2000 season, and moved to Jokerit for the next two seasons. In 2002, he returned to HIFK for one more season. He was drafted by the Chicago Blackhawks in the 2001 NHL Entry Draft, as their first-round pick, ninth overall. He then moved to North America in 2003, playing a full 82 games with the Blackhawks in the 2003–04 season.
Ruutu did not play during the 2004–05 NHL lockout, opting to take the time to recover from injuries, but provided commentary on Finnish television during the 2005 IIHF World Championship, along with fellow Finnish NHLer Ville Nieminen. Ruutu returned to the NHL after the lockout but his 2005–06 season was cut short, first by a back injury that kept him out of the game for most of the fall, then by an ankle injury sustained in January that required season-ending surgery.
After an unimpressive showing at the 2006 IIHF World Championship, Ruutu contemplated retirement from playing professionally. However, this notion was put to rest when Ruutu signed a two-year, $3.75 million contract extension with Chicago on 13 September.
During the 2007–08 season, on 26 February 2008, at the NHL trade deadline, the Blackhawks traded Ruutu to the Carolina Hurricanes in exchange for Andrew Ladd. The Hurricanes promptly signed Ruutu to a one-year contract worth $2.25 million.
On 23 July 2009, the Hurricanes signed Ruutu to a three-year, $11.4 million contract extension, paying $3 million in 2009–10, $4 million in 2010–11 and $4.4 million in 2011–12.
On 22 February 2012, the Hurricanes signed Ruutu to a four-year contract extension worth $19 million. The deal paid Ruutu $4 million in 2012–13 and $5 million per year in the remaining years; it also included a no-trade clause for the first three years of the contract.
Just hours before the end of the NHL trade deadline on 5 March 2014, Ruutu was traded to the New Jersey Devils in exchange for centre Andrei Loktionov.
In the 2015–16 season, Ruutu could not stay healthy and tallied one assist in the final game of the season. Ruutu was not re-signed by the Devils once his contract expired, becoming an unrestricted free agent on 1 July 2016. After going through the summer unsigned, Ruutu agreed to a professional tryout with the Vancouver Canucks on 13 September.
On 11 October 2016, Canucks general manager Jim Benning announced Ruutu had been released from his PTO contract.
On 28 October 2016, Ruutu was signed by HC Davos for the remainder of the season as a replacement for the injured Daniel Rahimi. He made his NLA debut on 11 November 2016 and scored his first goal that same day in a 3–2 loss in Geneva against Genève-Servette HC.
Tuomo Ruutu