The 23-year-old forward, who was a restricted free agent, had 40 points (14 goals, 26 assists) in 78 regular-season games and five assists in 14 Stanley Cup Playoff games for the Hurricanes last season.
"Martin is a dynamic young playmaker," Carolina general manager Don Waddell said. "He has an elite combination of speed and skill and we think he'll only continue to improve."
Selected by the Hurricanes in the first round (No. 12) of the 2017 NHL Draft, Necas has 119 points (45 goals, 74 assists) in 203 regular-season games, and 14 points (three goals, 11 assists) in 33 playoff games.
Carolina previously signed defensemen Ethan Bear (July 28) and Maxime Lajoie (Aug. 6) to avoid an NHL salary arbitration hearing with each. Defensemen Brent Burns and Dylan Coghlan, and forward Max Pacioretty were acquired July 13.
The Hurricanes (54-20-8) finished first in the Metropolitan Division last season, losing in seven games to the New York Rangers in the Eastern Conference Second Round.
