The team did not disclose terms, but sources told ESPN NFL Insider Adam Schefter it is a four-year, $48 million extension that includes $40 million in guaranteed money. Including the extension, Fisher now has $63 million left on his six-year deal.
Fisher, 25, who has started 30 games the past two seasons, is now set to remain entrenched as the Chiefs' starting left tackle, as he is tied to Kansas City through 2021.
"In three seasons he's grown significantly as a football player in our system," Chiefs general manager John Dorsey said in a statement. "He's a tough, physical presence and a leader on our offensive line. We look forward to keeping him as a part of our organization and community."
The two sides kept the deal as quiet as almost any recent blockbuster deal in the NFL and finished it in the opening days of camp.