New Celtic signing Nadir Ciftci made an instant impact as he set up Gary Mackay-Steven to score the winner against David Moyes' Real Sociedad.
The friendly was Celtic's final warm-up before they host Stjarnan of Iceland in Wednesday's Champions League qualifier.
And they came through unscathed in terms of injuries and with a confidence-boosting 1-0 win.
After replacing Leigh Griffiths, Ciftci fed the ball to Mackay-Steven who fired home on 68 minutes past Geronimo Rulli.
The Sociedad goalkeeper then produced a fine save minutes later to deny Ciftci, who completed a £1.5m transfer from Dundee United on Thursday.
Celtic had taken their pre-season friendlies to St Mirren Park because of work on their own pitch surface, and had already beaten Dutch outfit Den Bosch 2-0 and lost 5-3 to Dukla Prague of the Czech Republic.
Saidy Janko, the 19-year-old Swiss youth international full-back signed from Manchester United, also started on the bench for Ronny Deila's side against Sociedad.
The Spaniards, managed by former Celtic defender and Manchester United boss Moyes, had the better of the first half.
However, the Scottish Premiership side were brighter after the break, although a wave of substitutions disrupted play.