The ex-Wigan Athletic boss guided the unfashionable Toffees to a fifth-placed finish - with a record points haul - in 2013/14.
"I am delighted to have been given the opportunity to make a further commitment to Everton," Martinez told Everton's official website.
"I loved my first season at the club. I could not be more proud of the way Everton performed throughout the entire season and the memories we were able to make together.
"I am really excited about next season. I knew from the moment I arrived at Everton that this was a special place and I’d like to thank everyone associated with the club, the board, all the staff, the players and our brilliant supporters for believing in me and giving me the opportunity to build on the traditions and success of this great club."
Club chairman Bill Kenwright added: "In many commentators’ eyes, Roberto Martinez is the best young manager in Europe. We agree. He took on an unfamiliar challenge for most managers; to take something really good and make it even better.
"He has succeeded. In his debut season he broke our Premier League record points haul, got us back into Europe and developed some of the most exciting young footballers in the game.
"He conducts himself off the pitch in the same way. He undertakes his business with great style, confidence, positivity and class. He is an Everton man.
"Unswervingly, we trust Roberto Martinez to take our club forward. To use one of his favourite words we are ‘excited’ about our future. We have Roberto at the helm. Solo lo mejor!"