Knowledge of the effect of mining developments on caribou Rangifer tarandus is fragmentary. We examined the impact of the Hope Brook gold mine, southwestern Newfoundland, on the La Poile woodland caribou herd on a section of their year-round range. We examined the impact of the mine on caribou distribution during three phases of mine activity (pre-disturbance, construction and open-pit mining and underground mine and mill operation) in five seasons (winter, late winter, pre-calving, calving and autumn). Aerial surveys were conducted on a monthly basis from September 1985 to July 1991. Following initiation of the mine construction, caribou abundance increased with distance from the mine site in all seasons, and caribou avoided areas within 4 km of the site in most seasons. Within 6 km of the mine centre, group size and the number of caribou decreased as mine activity progressed in late winter, pre-calving and calving seasons. Although the impact of the mine was most prominent in the pre-calving and calving seasons, caribou responded to mine disturbance in all seasons. This highlights the importance of evaluating the year-round impact of human-induced environmental change.