Five-time Olympian Poulin missed her side's last two games after suffering a knee injury in Canada's 5-1 win over the Czech Republic on Monday, but returned in style to score her 18th Olympic goal, equalling the record of fellow Canadian Hayley Wickenheiser.
Canada saw off Germany with Brianne Jenner and Claire Thompson scoring in the opening period. Sarah Fillier and Blayre Turnbull added to the scoreline before Franziska Feldmeier scored for the Germans, with Poulin finding the net with less than five minutes left.
The US are already through to the last four after a 6-0 win over Italy, along with Sweden, who beat the Czechs 2-0.
Teams will be reseeded after the quarter-final matches are done to determine the semi-final pairings.