Calum Gallagher's penalty secured a bonus point for Arbroath.
Premiership St Mirren lost on penalties to second-tier Arbroath in their Premier Sports Cup opener.
The teams could not be separated in the 90 minutes, which the Buddies had to play out with 10 men after Mark O'Hara's second booking on 88 minutes.
Arbroath had converted all of their penalties before Fraser Taylor's spot-kick was saved by Aidan McAdams.
And that allowed Calum Gallagher to net the winning spot-kick for the hosts.
Arbroath take two points, St Mirren one. Elsewhere in Group D, there was another penalty shootout to decide Annan Athletic and Forfar Athletic's encounter. The sides drew 1-1 and visitors Forfar won 4-2 on spot-kicks.
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Buddies fans, were you at the game on Saturday? What did you make of the performance?
