Aberdeen secured a victory in their first Premiership match under the guidance of Jimmy Thelin, which ended Geoff Brown's tenure at St Johnstone on a sour note.
The new Dons boss followed up his unbeaten League Cup group stage campaign with a convincing display at McDiarmid Park on the night the hosts paid tribute to their former owner.
Nicky Devlin headed home the opener with Jamie McGrath doubling their lead after the break with a clinical finish.
St Johnstone, who lost Sam McClelland to injury, were given hope by Gavin Molloy's own goal but they could not find an equaliser despite a late spell of pressure.
Thelin is the first Aberdeen boss to win his first five games in charge as Craig Levein's new signings failed to shine.
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