Rupp scored in the second period and got his other two goals, one unassisted, in the third. The seven-year veteran, who had just three goals all of last season, has eight this year.
Sidney Crosby notched the other two goals and added an assist for the Penguins, who have won five of their last six games.
Marian Gaborik produced both New York goals.
Pittsburgh goalie Marc-Andre Fleury made 29 saves and the Rangers' Henrik Lundqvist had 28.