During the 1940's, Jean-Paul Sartre published a multitude of philosophical works dealing with human understanding. At the end of Being and Nothingness , his magnum opus, Sartre promised a moral theory. By 1947, he had filled a dozen notebooks bearing on moral theory, but because he was unsatisfied with his work they were never published during his lifetime. By using the ontology Being and Nothingness and Notebooks for an Ethics , combined with the help of Sartre's other philosophical works of the same period, I demonstrate that a moral theory based on Sartre's philosophy is possible; unlike what many of his critics have claimed. In order to do so, I look at the influence made by German philosophers on Sartre's early work; some of the most important elements of his philosophy in relation to his moral theory; a critical assessment of criticism held against a Sartrean moral theory; and finally how such a model could function.