On April 28, 2014, the Seattle Seahawks signed Thomas to a four-year, $40 million contract extension with $27.72 million guaranteed and a signing bonus of $9.50 million.

On November 9, 2014, Thomas recorded six combined tackles, deflected a pass, and made his only interception of the season during a 38–17 victory against the New York Giants in Week 10.
Thomas intercepted a pass by quarterback Eli Manning, that was intended for wide receiver Odell Beckham Jr., and returned it for a 47-yard gain in the fourth quarter.
In Week 17, he collected a season-high 12 combined tackles (11 solo) in the Seahawks' 20–6 win against the St. Louis Rams.
On December 23, 2015, Thomas was announced as a selection to play in the 2016 Pro Bowl.
He finished the season with 97 combined tackles (71 solo), five pass deflections, three forced fumbles, and an interception in 16 games and 16 starts.

The Seahawks had the top-ranked defense in the NFL in fewest points allowed for the third straight season and finished atop the NFC West with a 12–4 record.
On January 10, 2015, Thomas collected 11 combined tackles (five solo), two passes defended, and a forced fumble as the Seahawks defeated the Carolina Panthers 31–17 in the Divisional Round.
The following week, he made five combined tackles, but suffered a dislocated shoulder in the second quarter of their 28–22 victory against the Green Bay Packers in the NFC Championship.
On February 1, 2015, Thomas recorded nine combined tackles in the Seahawks' 28–24 loss to the New England Patriots in Super Bowl XLIX.
On April 28, 2014, the Seattle Seahawks signed Thomas to a four-year, $40 million contract extension with $27.72 million guaranteed and a signing bonus of $9.50 million.
On November 9, 2014, Thomas recorded six combined tackles, deflected a pass, and made his only interception of the season during a 38–17 victory against the New York Giants in Week 10. Thomas intercepted a pass by quarterback Eli Manning, that was intended for wide receiver Odell Beckham Jr., and returned it for a 47-yard gain in the fourth quarter. In Week 17, he collected a season-high 12 combined tackles (11 solo) in the Seahawks' 20–6 win against the St. Louis Rams. On December 23, 2015, Thomas was announced as a selection to play in the 2016 Pro Bowl. He finished the season with 97 combined tackles (71 solo), five pass deflections, three forced fumbles, and an interception in 16 games and 16 starts. 
The Seahawks had the top-ranked defense in the NFL in fewest points allowed for the third straight season and finished atop the NFC West with a 12–4 record. On January 10, 2015, Thomas collected 11 combined tackles (five solo), two passes defended, and a forced fumble as the Seahawks defeated the Carolina Panthers 31–17 in the Divisional Round. The following week, he made five combined tackles, but suffered a dislocated shoulder in the second quarter of their 28–22 victory against the Green Bay Packers in the NFC Championship. On February 1, 2015, Thomas recorded nine combined tackles in the Seahawks' 28–24 loss to the New England Patriots in Super Bowl XLIX.
Earl Thomas