Joe Bradley's first goal for Queen's Park put the League Two side into Petrofac Training Cup quarter-finals at the expense of Dumbarton.
The former Beith juniors forward swept home Vinnie Berry's low cross in the first-half of extra time at Hampden.
Dumbarton spurned a great chance when Garry Fleming blasted a penalty well over close to the 90-minute mark.
Spiders goalkeeper Willie Muir tipped Willie Gibson's free-kick round the post as the Sons came up short.
Dumbarton came into this tie brimming from a perfect start to their league campaign - wins versus Hibernian and St Mirren giving them six points from six.
But it was laboured play for much of the night from Stevie Aitken's men, which allowed Queen's Park to gradually settle.
Substitutes Bradley, John Carter and Ciaran McElroy - with trickery and endless running - each played crucial roles in helping Gus Macpherson's side progress.
- 10BatyBooked at 108mins
- 5GibsonBooked at 90mins
- 7WoodsSubstituted forMcElroyat 87'minutesBooked at 91mins
- 9MortimerSubstituted forBradleyat 45'minutes
- 11MarlowSubstituted forCarterat 30'minutes
- 2TaggartBooked at 107mins
- 5BuchananBooked at 32mins
- 16WatersSubstituted forDochertyat 58'minutes
- 10KirkpatrickSubstituted forCraigat 58'minutes
- 17RoutledgeBooked at 93mins
- 11SmithSubstituted forGibsonat 59'minutesBooked at 89mins
- Nick Walsh
- Shots on Target