self.plot = self.addPlot()
self.plot.setLabels(left="Left axis")
font = self.plot.getAxis("left").label.font()
font.setFamily("Serif")
self.plot.getAxis("left").label.setFont(font)
self.plot.getAxis("left").setTickFont(font)font = self.plots[key]["item"].titleLabel.font()
font.setFamily("Serif")
self.plots[key]["item"].setFont(font)
self.plot = self.addPlot(title="Plot title")
font = self.plot.titleLabel.item.font()
font.setFamily("Serif")
p1.titleLabel.item.setFont(font)I think the issue is that the reference to titleLabel is actually a LabelItem object, so you then need to dig into it to get the reference to item, which is the QGraphicsTextItem object within.
Patrick