Arrieta struck out 11 without a walk. He also dusted off getting plunked by Pittsburgh reliever Tony Watson to send the Cubs to the NL Division Series in St. Louis starting on Friday.
Dexter Fowler homered and scored three times for the Cubs. Kyle Schwarber added a towering two-run shot off Pittsburgh starter Gerrit Cole as Chicago raced to an early lead and let Arrieta do the rest.
The largest crowd ever at PNC Park failed to rattle Arrieta or one of baseball's youngest teams. Manager Joe Maddon's club played with swagger and confidence and looked right at home while snapping a nine-game playoff losing streak that dated to the 2003 NL Championship Series.