Montrose gave new manager Paul Hegarty victory in his first home game and kept alive their hopes of avoiding bottom spot in League Two.
The defeat leaves Arbroath still looking for their first win of 2015 and sees them slip further behind the division’s top two, Albion and Queen’s Park.
Hegarty said: “We deserved to win and my players were excellent. I asked them to do certain things and they carried them out.
“All the players were heroes and they scored excellent goals. Graham Webster has just come back from the juniors and his goal was a wonderful finish.
“We could have had more as we had a few chances midway through the second half.
“My keeper and back four were outstanding and showed they know how to defend, but we have a long way to go to peg back the teams above us.
“We have got off the mark and the manner in which we did so will give us a lot of confidence.
“The team that is the first to drop out of the league through the new play-offs will be remembered and we do not want it to be us. We know it will be difficult, but we must continue to show the same spirit.”
Montrose were on top from the start and a Garry Wood overhead-kick dipped just over, then a bullet header from Marvin Andrews was just too high.
On 23 minutes, Bobby Linn made space for a shot and home keeper Stuart McKenzie made the first of a number of saves.
Paul McManus missed a sitter from a Linn cross and Arbroath were made to pay when Montrose took the lead on 28 minutes. Ross Campbell slipped the ball through and Webster slammed it high into the net.
McManus missed another gilt-edged chance from a Carreiro cutback, then a Ross McCord shot forced a great save from Marc McCallum.
Just on half-time, a shot from Kieran Stewart was turned round the post by McKenzie.
Montrose stretched their lead on 48 minutes. Wood laid the ball off to Campbell and he found the bottom corner.
McKenzie made another save from Linn and Montrose went upfield to stretch their lead on 52 minutes. A cross from Webster was headed back by Scott Johnston and Campbell shot home.
On 61 minutes, Wood flicked the ball against the post from close range.
Eight minutes later, Kevin Buchan hit the bar for Arbroath.
Arbroath boss Alan Moore appealed for the fans to stay with his side as they go for promotion.
“I am sorry for our support as they have seen their side lose a local derby.
“In the first half we were well in it and the game hinged on chances which were not taken. They scored with their first shot on target so it is a fine line.
“Things are not going our way, but it was poor defending for the second goal when we didn’t pick up the runners.
“I took the praise earlier in the season so I will take the stick now. We have got to pick ourselves up for our next game against Clyde.
“We are still in there fighting. Goals win games and we are not sticking our chances away.
“We have to stay calm and regroup as we can still finish top.
“The players will not play any better if the fans turn on them. We need them there to back us.”