In Atlantic Canada, bulk-sediment dates for the onset of a late-glacial cooling, widely regarded as the Younger Dryas event, are highly variable, ranging from 14,300 ± 270 to 10,800 ± 100 yr B.P. We present the first accelerator-mass-spectrometer (AMS) 14C dates from Atlantic Canada, at or close to the boundaries of this event, from six sites in New Brunswick and Nova Scotia. The mean of five dates places the onset of this cooling at ca. 10,770 yr B.P.; the inclusion of a sixth, perhaps anomalously old date, changes the mean to 10,880 yr B.P. The termination averages (three dates) ca. 10,000 yr B.P. These dates place the timing of the Younger Dryas event in Atlantic Canada closer in line with the traditional chronozone boundaries of 11,000 and 10,000 yr B.P. in Northwest Europe.