We discuss paleoenvironmental changes at the Dae-Am San high moor, located near the Demilitarized Zone at 38°N. This area has been reported to be the only high moor in the Korean peninsula. The 14C age of the bottom sediment (75–80 cm in depth) at this site is about 1900 BP. Since the radiocarbon ages for the intervals at 50–55 cm and 75–80 cm were almost the same, we conclude that the deep layers (55–80 cm) in the high moor were all part of the original soil. Low organic C and N contents in the deeper layers support this inference. The 50–55-cm layer consists of sandy material with very low organic content, suggesting erosion from the surrounding area. The surface layer (0–5 cm) was measured as 190 BP, and the middle layer (30–35 cm) was 870 BP. The bulk sedimentation rate was estimated to be about 0.4 mm yr−1 for the 0–30-cm interval. The δ13C value of organic carbon in the sediments fluctuated with depth. The δ13C profile of the Dae-Am San high moor may be explained by climatic changes which occurred during the Little Ice Age and Medieval Warm Period.