Motion sickness is generally caused by not being able to correctly estimate one’s self-motion. In the case of crew in, e.g., the command centre of a naval vessel, a nauseating conflict exists between what they see (the stable interior of the ship) and what they feel (the motion of the ship). To reduce the conflict, we designed and tested an ‘anti-seasickness display’ presenting visual motion in the opposite direction of the ship’s motion, thus effectively presenting an Earth-fixed frame of reference. Fourteen subjects completed a number of 20-minute trials in TNO’s motion simulator Desdemona, which reproduced a realistic ship motion. The anti-seasickness display consisted of a three-dimensional virtual world of stars. It was presented on a laptop monitor in the background of a partially transparent demanding computer task in a number of conditions, and on a panoramic screen in front of the participant in another. The task was added to also study a possible effect on task performance, either negatively by interference of the stars with the computer task, or positively by the anticipated reduction of motion sickness. Sickness severity was rated at fixed intervals. Results show that the anti-seasickness display reduced sickness due to ship motion, whether presented on the computer monitor or on the panoramic screen. No effect on task performance was found, thus the graphics of the anti-seasickness display did not interfere with the task used in this experiment. We conclude that anti-seasickness displays providing a spatial Earth-fixed reference to correctly estimate one’s self-motion, appear to be a promising solution to reduce seasickness.