Icebreaker vessels are important scientific tools, enabling access and research within the polar regions of the world, including the High Arctic. These vessels have the potential to overlap with marine mammal habitats in infrequently studied areas. Marine mammal behavioral responses to icebreaker vessel presence and distance at which responses occur are not well documented or understood. During the Petermann 2015 Expedition on the icebreaker Oden, seal and polar bear (Ursus maritimus) data were collected in Petermann Fjord (Northwest Greenland), the adjacent Nares Strait region, and transit to and from Thule, Greenland over 31 days (July 30 to August 30, 2015). We examined behavioral responses from 4 pinniped species: bearded seal (Erignathus barbatus), ringed seal (Pusa hispida), harp seal (Pagophilus groenlandicus), and hooded seal (Crystophora cristata), as well as the polar bear to an icebreaker vessel in a rarely studied region of northwest Greenland. We investigated the rate of flush response, entering the water from a previously hauled out (i.e., resting) location on ice in relation to seal distance to the vessel. Our results showed a significant difference (independent t-test, P ≤ 0.001) between seal distance to the vessel when a flush response occurred (mean = 467.1 m, SD = 212.39 m) and when no flush response occurred (mean = 1334.0 m, SD = 433.89 m). There were fewer flush responses by seals to the icebreaker at distances >600 m and no flush responses by seals to the icebreaker at distances >800 m. We used a logistic model to describe the relationship between the proportion of seals that flushed and distance from the icebreaker. Results of the logistical model showed the estimated distance at which 50% of the seals flushed to be 709.45 m (SE = 9.24, t = 76.8, P < 0.0001). Three polar bears were recorded during the transit, and a behavioral response (e.g., look, approach, move away) was recorded for all 3 sightings. Our preliminary findings are relevant to assess potential impacts of increasing vessel activity in the High Arctic and to assist in the development of effective monitoring and mitigation strategies.