Back-to-back home runs from Nolan Arenado and Trevor Story in the top of the eighth inning saw the Rockies claw their way back to within one run of the D-Backs at 8-7.
But A.J. Pollock’s triple for Arizona in the bottom of the eighth allowed J.D Martinez and Jake Lamb to score and gave the Diamondbacks’ breathing space at 10-7.
Pollock then scored after Jeff Mathis reached base on a bunt off pitcher Greg Holland to put the Diamondbacks 11-7 ahead.
The Rockies clawed a run back after Carlos Gonzalez’s single saw Ian Desmond score in the top of the ninth but it was not enough.
Arizona will now advance to a NL best-of-five playoff series against the Dodgers, who had the best record in the major leagues this season, with game one on Friday.
Earlier, Arizona seized a 3-0 lead in the first inning as David Peralta and Ketel Marte singled before Paul Goldschmidt smashed a three-run homer, blasting a hanging curve ball from Colorado right-hander Jon Gray over the left-field wall.
The Diamondbacks boosted their margin to 4-0 in the second inning when Peralta singled and scored on a triple to the center field wall by Dominican shortstop Marte, prompting Colorado to remove Gray from the mound.
Daniel Descalso blasted a two-run homer to the rightfield stands in the third inning to stretch Arizona’s edge to 6-0.
The Rockies finally responded in the fourth when Arenado reached on a fielder’s choice, took second on Story’s single and scored on Gerardo Parra’s single to centerfield.
Story scored for third base when Mark Reynolds grounded out to first base and Jonathan Lucroy smacked a line drive double to right field to score Parra and pull Colorado within 6-3.
Moments later, Alexi Amarista smacked a single up the middle to score Lucroy, lifting the Rockies within 6-4 and prompting Arizona to remove starting pitcher Zack Greinke after the shortest playoff start of his career.
Lucroy pulled the Rockies within 6-5 in the seventh when he doubled, took third base on a wild pitch and scored when Charlie Blackmon hit a sacrifice bunt to second base.
Arizona struck for two runs in the seventh after Jake Lamb singled, Daniel Descalso walked and Archie Bradley smacked a two-run triple to centerfield, boosting the Diamondbacks’ edge to 8-5.
The Diamondbacks-Dodgers winner will face either Washington or the defending champion Chicago Cubs in the National League finals to decide a berth in the World Series.
The American League playoffs continue Thursday with Boston at Houston and the New York Yankees at Cleveland in the openers of their best-of-five matchups.