A decreasing trend in narwhal (Monodon monoceros Linnaeus, 1758) abundance has been identified in a small population in Scoresby Sound, Southeast Greenland. We hypothesize that excessive hunting has affected life history and population dynamics of this population. Biological information and samples collected from the Inuit hunt, from satellite-tagged narwhals and from official hunters’ reports, were used to estimate age, growth, and reproduction. During 2007 through 2019, a decreasing proportion of young and increasing proportion of older whales were harvested. Male and female body length and male tusk length increased significantly, while body mass of both sexes showed a nonsignificant increase. The probability of catching a female decreased significantly, while a nonsignificant decline of catching a pregnant female was observed in both biological samples and hunters’ reports. Narwhal swimming speeds correlated with fluke widths indicated that larger whales attain greater speeds. The decline in juveniles and females is probably due to an opportunistic hunting practice targeting the easiest-to-catch whales, where bigger whales are faster and more difficult to catch. The cumulative effect of overharvest with a declining proportion of females, an overrepresentation of large males, and a lack of calves and juveniles has detrimental implications for this small narwhal population.