On January 3, 2018, Stamkos was voted by fans to be the Atlantic Division captain at the 2018 National Hockey League All-Star Game, which was held at the Lightning's home arena, Amalie Arena. This was Stamkos' fifth NHL All-Star Game appearance, which moved him past Vincent Lecavalier for second most NHL All-Star Game appearances by a Lightning player. On January 25, 2018, Stamkos recorded his 300th career NHL assist. The milestone came in a 5–1 Lightning victory over the Philadelphia Flyers away at the Wells Fargo Center. On February 8, Stamkos recorded his 20th goal of the season, which came in a 5–2 win over the visiting Vancouver Canucks. This was Stamkos' ninth 20-goal season in franchise history, which tied him with Martin St. Louis for second-most such seasons in franchise history. On March 3, Stamkos set a new career high with a five-point game in a 7–6 Lightning shootout win over the visiting Flyers. Stamkos became the seventh Lightning player in franchise history to score five points in one game. The five-point game also gave Stamkos the most career regular season games scoring at least four points in franchise history, with 11. On March 21, Stamkos was fined $5,000 for a dangerous trip against Toronto Maple Leafs' defenceman Morgan Rielly, which occurred the previous night at Amalie Arena. On March 30, Stamkos appeared in his 663rd career NHL game, which moved him past Pavel Kubina for third-most games played in Lightning history. On May 17, Stamkos recorded his 11th career NHL playoff power-play goal in a 4-2 Lightning win over the Washington Capitals at Capital One Arena. The goal moved Stamkos past St. Louis for most playoff power-play goals in franchise history.