They won the National Football Conference (NFC) Championship Game and played in Super Bowl XL, which they lost 21–10 to the Pittsburgh Steelers.
There, they beat the Washington Redskins and Carolina Panthers to win the George Halas Trophy, and advance to their first ever Super Bowl.
The offense was led by 7th-year veteran quarterback Matt Hasselbeck, who compiled a career-high and NFC leading 98.2 passer rating, while completing 65.5% of his passes, earning his second trip to the Pro Bowl.
Future Hall of Famers Walter Jones and Steve Hutchinson anchored the offensive line at left tackle and guard respectively, and Mack Strong effectively blocked and rushed from the backfield at fullback on his way to a 2005 All-Pro Team selection.
In the secondary, Michael Boulware led the team with four interceptions and also tallied two sacks and one fumble recovery, however Seattle suffered injuries throughout the year, notably to free safety Ken Hamlin.
A bright spot in relief, second-year cornerback Jordan Babineaux played well as he appeared in all sixteen games for Seattle, intercepting three passes and making 61 tackles.
[2] At the time of Whitsitt's firing the Seahawks salary cap situation was in extreme flux with 16 unsigned free agents on the roster including their three biggest stars Matt Hasselbeck, Shaun Alexander and Walter Jones.
On February 3 Mike Reinfeldt, who had previously been pushed out of the Seahawks organization by Whitsitt, was hired back as a consultant to try to sort out the mess.
[3] Reinfeldt was able to sign Jones and Hasselbeck to long-term deals and put the Franchise Tag on Alexander, setting the stage for the rest of the off-season.
After a careful executive search the Seahawks settled on highly regarded personnel man Tim Ruskell as the new President of Football Operations on February 23, 2005.
As a part of his roster overhaul, Ruskell subsequently released or neglected to re-sign six players (Anthony Simmons, Chad Brown, Orlando Huff, Chike Okeafor, Rashad Moore and Cedric Woodard) who were starters on an underperforming defense during the 2004 season.
Over the rest of the offseason and into training camp Ruskell signed a raft of free agents to replace departed players on both sides of the ball, emphasizing character and work ethic in his evaluations.
They then gave up two fourth-round picks to trade up into the second round and select USC linebacker Lofa Tatupu, who would start every game of the 2005 season and go to the Pro Bowl as a rookie.
On Atlanta's last drive Bryce Fisher sacked Michael Vick on third down, and on the next play, Andre Dyson knocked down Matt Schaub's 4th down pass.
The Seahawks' defense forced its first turnover of the season, including a fumble recovery following a sack of Josh McCown by Michael Boulware at the Arizona 1.
The defense recorded 2 takeaways in the second half, an interception by Lofa Tatupu and a fumble recovery on a punt by J. P. Darche with 2:51 left in the game.
After their Week 8 bye, the Seahawks traveled to Sun Devil Stadium and completed a season sweep of the Cardinals by a score of 33–19.
With the score tied 21–21, opposing kicker Jay Feely missed three chances for a winning field goal (one as time expired in regulation and two in overtime).
Seahawks gunslinger Matt Hasselbeck threw for 249 yards and two TDs in Seattle's 24–21 overtime victory over the New York Giants.
This game is also remembered for the raucous noise inside Qwest Field which caused 11 false start penalties against the Giants.
A fourth interception return by Michael Boulware fell just short of tying another Seahawks NFL record of four defensive scores in a single game, set during a 45–0 victory over the Kansas City Chiefs in 1984.
Matt Hasselbeck completed the fourth quarter comeback, throwing a game-winning 2-yard pass to wide receiver Bobby Engram.
After the Colts took the lead with a field goal, a kickoff return by Josh Scobey set up the Seahawks' first score, a 2-yard run by Alexander.
The Colts scored on a 6-yard pass from Jim Sorgi to Troy Walters to cut the lead to 28–13, but Scobey recovered the ensuing onside kick and Seattle ran out the clock to hold on for a 28–13 win.
On January 22, 2006, the team clinched its first Super Bowl berth in franchise history, with a commanding 34–14 win over the Carolina Panthers.
The Seahawks stormed out to a 17–0 lead before the Panthers' Steve Smith returned a punt 59 yards for a TD, making the score 17–7.
Entering the third quarter with 20–7 lead, Seattle took the opening possession of the 2nd half and scored on a Matt Hasselbeck to Bobby Engram TD pass.
Seattle fell short in its bid for its first NFL title, losing to the Pittsburgh Steelers at Super Bowl XL in Detroit, Michigan on February 5, 2006 by a score of 21–10.
Jason Whitlock, writing for the Kansas City Star, encapsulated many views when he wrote the day after the game, "Leavy and his crew ruined Super Bowl XL.
[10] On August 6, 2010, while visiting the Seahawks' preseason training camp for an annual rules interpretation session with the Seattle media, head official Bill Leavy brought up Super Bowl XL without being asked, while admitting to having blown calls:[11] It was a tough thing for me.