The aim of the article is to present sensitivity in the context of Jean-Paul Sartre’s existential thought. Based on the definition of sensitivity as the ability to react to stimuli, the author discusses three chosen types of reaction: feeling, premonition and compassion, and puts them in the perspective of the respective themes from Sartre’s philosophy of existence: being, time and relationship. The paper discusses the place and role of the concept of sensitivity in existentialism, arguing that every human being thrown into this world is forced to react to stimuli due to his or her existential construction. The author also introduces the concept of existential sensitivity – a logical consequence of our life to which we are all condemned.