Cubs rookie Kris Bryant had four hits, raising his spring average to .459.
The Cubs scored seven times in the first inning, helped by four plays that Colorado botched and Arrieta's three-run homer.
Bryant hit a double off starter Jonathan Gray, who left after getting only two outs.
Second baseman Charlie Culberson and catcher Michael McHenry made errors, a bunt was fumbled and no one covered first base on another bunt.
''After the first two hitters of the game, it went downhill from there,'' Rockies manager Walt Weiss said.
Arrieta gave up three hits, walked none and struck out five.
Along with his homer, Arrieta got a double when his long fly to center field was lost in the sun by Drew Stubbs.
Arrieta was more than happy to talk about his plate prowess.
''We put time into it,'' Arrieta said of the pitching staff's hitting.
Cubs pitchers want to ''kind of catch up'' with teammate Travis Wood, one of the game's best-hitting pitchers.
''He sets the standard pretty high,'' Arrieta said. ''We have a friendly competition at the plate and try to really put together some good at-bats and kind of challenge each other and contribute as much as we can.''
Rockies: Gray, a candidate for a rotation spot, gave up six earned runs and four hits. He walked one and struck out two.
''He was 40 pitches in,'' Weiss said. ''You don't want a guy to go any more than that in one inning. So I got him out of there.''
''He made it tough on himself on a couple of bunts back to him. We didn't play well behind him,'' he said.
In the longer view, ''he's come a long way,'' Weiss said. ''He's had a great spring. It was really a strange inning. It's one inning of many, many he's going to throw.''
Cubs: Arrieta threw 30 pitches afterward in the bullpen.
Rockies: Three infielders who had been nursing injuries returned to action. Culberson hadn't played since March 8, Daniel Descalso since March 14 and Justin Morneau since Wednesday.
Cubs: A decision on whether outfielder Chris Denorfia, who is working through a hamstring injury, can make the opening day roster should be made within days, manager Joe Maddon indicated.
SOLER A SURE BET
There are debates and discussions on whether the Cubs will, or should, have Kris Bryant and Javier Baez on the opening-day roster.
But there are no such questions about Jorge Soler.
At 23, he's sure to be the starting right fielder. And he's a candidate, along with Chris Coghlan, to hit second in the lineup.
''With him, it goes beyond just his power,'' Maddon said. ''This guy has great decision-making ability at the plate.
''He's a really interesting baseball player. If he had been in the United States as a draft choice (Soler is from Cuba), my God, he's the No. 1 pick, no doubt.''
''He's the whole package. He's got the best throwing arm out of the whole (outfield) group. He's accurate. His mechanics, technique are really good, too. I think he's going to be a really good outfielder.''
Rockies: Jordan Lyles is scheduled to start Sunday vs. Arizona.
Cubs: Edwin Jackson is set to start Sunday at the Kansas City Royals in Surprise. He missed his last scheduled start when he went to the wrong ballpark to face Oakland - the A's have a new spring home this season.