On 14 October 2017, in a game against the Boston Bruins, Ekman-Larsson scored his first powerplay goal of the season against Anton Khudobin and moved ahead of Fredrik Olausson for the franchise record for powerplay goals scored by a defenceman with his 41st. On 10 January 2018, Ekman-Larsson was selected as the lone Coyotes representative at the 2018 NHL All-Star Game. On 10 March, Ekman-Larsson was fined $5,000 for slashing Sven Andrighetto. After the regular season concluded and the Coyotes again failed to make the playoffs, Ekman-Larsson was nominated for the King Clancy Memorial Trophy, awarded to the player who best exemplifies leadership qualities on and off the ice and gives back to his community. On 1 July 2018, Ekman-Larsson signed an eight-year, $66 million contract extension with the Coyotes; he was set to become a free agent the following season. He was later named captain of the Coyotes.