The NHL made helmets mandatory for players entering the league in 1979.
The rule was announced in August 1979 and took effect with the 1979–80 season. It required new NHL players to wear protective helmets, reflecting growing concern about head injuries and the dangers of high-speed collisions, sticks, and pucks. The rule did not immediately require every veteran to wear one.
Players who had signed professional contracts before June 1, 1979, could continue playing without a helmet if they signed a waiver. This grandfather clause explains why helmetless players remained visible in NHL games for many years after the rule began. Craig MacTavish of the St. Louis Blues was the last helmetless NHL player, retiring after the 1996–97 season.
The rule is often misstated as a universal helmet mandate beginning in 1979. More precisely, 1979 marked mandatory helmets for players entering the NHL, while experienced veterans with grandfathered status could opt out. A later rule also addressed what players must do if their helmet comes off during play.