DENVER — Corey Dickerson didn't miss when he got a second chance to come through.
It was the second big hit of the night for Dickerson, who sent the game into extra innings with a home run to the third deck in the ninth.
"It's one of the longer ones I've seen here," Rockies manager Walt Weiss said. "I've seen a few go into that upper deck but he hit that ball a long way. He can hit. It's well documented."
Matt Belisle (4-6), the ninth Rockies pitcher, got the win with one inning of perfect relief.
Arenado led off the 13th with a double off the wall in left field against Sam Dyson (2-1). Dickerson, who was bested by Dyson on Friday, followed with a liner to right, and Arenado easily beat the throw from Giancarlo Stanton.
"Last night, bases loaded, same guy and I swung first pitch on a sinker and grounded out," Dickerson said. "I kind of wanted to see a pitch and I wanted to get a pitch up. He threw a ball down like last night, and I think he hung a changeup or a slider up and in."
His teammates mobbed him near second base after he ended the 4 hour, 28-minute game.
It was the sixth walk-off win for the Rockies this season.
"We put ourselves in a good position, had a chance to win a ballgame and it didn't happen," Miami manager Mike Redmond said. "We had it and we just couldn't lock it up."
Adeiny Hechavarria gave the Marlins a 4-3 lead in the ninth with an RBI single off closer LaTroy Hawkins. Dickerson tied it in the bottom half with a 455-foot drive off Steve Cishek for his 19th homer of the season. It was Cishek's fourth blown save.
"I fell (behind) 3-1 to a guy that's an all-or-nothing hitter, and when you miss down and in to a lefty that's a power hitter, it doesn't put you in a good spot or the team in a good spot," Cishek said.
The Rockies erased a 1-0 deficit in the third inning with a run on a double play and a two-run homer by Brandon Barnes.
Miami got a run in the fourth when Jordan Lyles walked Donovan Solano with the bases loaded, and then tied it on Jarrod Saltalamacchia's RBI double in the fifth.
Lyles left after giving up a pair of two-out singles in the sixth, but lefty Rex Brothers struck out Garrett Jones to end the inning.
Lyles allowed three runs on seven hits, struck out five and walked five.
Miami starter Tom Koehler's only blemish was the third inning. He struck out four and didn't walk a batter in tossing seven solid innings.
After allowing two singles to lead off the fourth he retired 11 of the last 12 batters he faced. The one single he allowed was wiped out on a caught stealing.
Dickerson's home run was the 33rd to reach the third deck in Coors Field. The last player to do it was Brandon Moss on June 12, 2012, for Oakland. The last Colorado player to do it was Carlos Gonzalez as part of his cycle on July 31, 2010.
"I've done it a couple of times in (batting practice) and just joking around they tell me to do it in a game," Dickerson said. "I got a good pitch and put a pretty good swing on it."
Hechavarria saved a run in the bottom of the 12th when he raced out and made a leaping catch of Justin Morneau's blooper with two outs. Had the ball fallen Rockies pitcher and pinch-runner Tyler Matzek would have scored from third.
"I don't how he got to that ball. At the time, it was a huge game-saving play," Redmond said. "It's too bad we couldn't come back and flip a run out there, but it wasn't our night."
The Marlins had a rally going in the 11th when the first two batters reached. But the inning turned strange when Marcell Ozuna's line drive went off the glove of shortstop Josh Rutledge. Rutledge got the ball and tagged second for one out, and Casey McGehee was caught between second and third. He was tagged out in a rundown.
"I was just trying to get a ground ball out there and it ended up being a line drive," Rockies reliever Nick Masset said. "I was saying, 'Tag the guy, no tag the base.' Just excited about the way it went."
Marlins: No injury updates.
Rockies: OF Michael Cuddyer didn't start for the fourth consecutive game because of a sore left hamstring. Cuddyer pinch-hit in the 12th and drew a leadoff walk.
The Marlins will send LHP Brad Hand (2-5, 4.52) against RHP Christian Bergman (0-2, 7.20) in the last game of the three-game set. Bergman is making his first start since breaking his left hand in a start against Milwaukee on June 20.