Research suggests new foreign language (FL) words are learned more easily if their phonology follows the phonotactic rules of the native language. Very little is known, however, about the impact of orthography on FL learning. This study investigated the cognitive mechanisms supporting the learning of words with familiar and unfamiliar orthographies. Participants took part in learning and meaning recall tasks, as well as a series of cognitive tasks (short-term and working memory tasks and tasks assessing their phonological and acoustic abilities). Orthographic and phonological familiarity judgments were collected using another sample of participants. Using a mixed-effects model, the results showed that orthographic familiarity impacted FL word learning even after controlling for phonological familiarity. However, there were no interactions with cognitive abilities.