Terms were not disclosed. The deal puts Seumalo under contract through the 2022 season.
Seumalo, 25, is the second Eagles starting offensive lineman to receive an extension this offseason, joining center Jason Kelce, who agreed to a one-year extension on Saturday that put him under contract through 2021.
The Eagles also signed defensive end Brandon Graham to a three-year extension last week, keeping him from testing free agency.
Seumalo missed the last three games of the regular season with a pectoral injury but returned for the postseason, starting both of the Eagles' playoff games. He took over for Stefen Wisniewski as the Eagles' starter at left guard in Week 5 last season.
Seumalo, who was drafted in the third round (79th overall) of the 2016 draft, had one season remaining on his rookie contract.