In March of this year 96.8 per cent of people were seen within four hours, but in April the figure dropped marginally to 96.2 per cent.
The statistic bucks a national trend of a reduction in waiting times.
However, it is an improvement on the same time last year when 95.8 per cent of patients were seen within four hours.
Commenting on the figures, a spokesman for NHS Dumfries and Galloway attributed the slight rise in accident and emergency waiting times to an outbreak of Norovirus which was first reported on Saturday March 28.
He said: “During the course of this week outbreak 46 patients and 12 staff reported symptoms.
“Wards nine, ten, 12 and 14 were all closed at points during the outbreak which created significant bed pressures.
“Staff worked hard to minimise the spread of this outbreak and maintain performance at a high level despite the ward closures.
“It is worth noting that of the mainland boards across the whole of Scotland only Tayside and Highland performed better against the accident and emergency waiting time target.
“We would like to thank staff for their efforts during this difficult time.”