USA international Howard, 35, has penned a deal keeping him at the Toffees until the summer of 2018.
The former Manchester United shot-stopper had been linked with a move to Premier League rivals Arsenal.
“It is fantastic news,” Martinez told evertontv. “To have Tim Howard performing as he has been this season, I cannot see past him to choose the best goalkeeper in the league.
“For him, in such an important year with the World Cup around the corner, to commit his future for the long term is an incredible moment for the dressing room.”
Howard has been at Everton since 2006.
He has kept over 100 clean sheets and is widely regarded as one of the most consistent keepers in the Premier League.
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