The Canadian, who was denied gold at Sochi 2014 by Eva Samkova, had already been crowned women's snowboard cross World Cup champion for the fourth season running.
But she fended off nearest World Cup rival Lindsey Jacobellis to take her third win of the year, while Bulgaria's Alexandra Jekova topped the small final to finish third in the overall standings.
Meanwhile, men's World Cup champion Omar Visintin could not match Maltais' final flourish after being knocked out at the quarter-final stages in Spain.
It was German Paul Berg who enjoyed a special day instead, clinching overall second with victory after failing to place on the podium all season.
Home favourite Regino Hernandez took the bronze with Canada's Christopher Robanske just behind, who ended the season third in the standings.
- Sports & Recreation
- Eva Samkova
- Alexandra Jekova