Background: Children and adults with developmental disability frequently require either aided or unaided alternative and augmentative communication (AAC). Key word sign (KWS) involves using natural gesture and sign language to support the key words in spoken utterances. The purpose of this study was to determine whether communication partners of children and adults with developmental disabilities can learn and retain a basic KWS vocabulary. Materials and Methods: Communication partners attended a one-day training workshop where they were taught 100 signs. Measures of sign recognition and production were taken prior to the training, immediately after the training on the day and at 6 and 12 weeks later. Results: Participants were able to learn signs during the workshop and demonstrate receptive and expressive knowledge of KWS. However, sign knowledge decreased after 6 and 12 weeks. Participants noted that having to be tested again after several weeks, motivated them to practise and served as a follow-up. Conclusion: This paper provides evidence that KWS training enables participants to learn and retain signs, but that there is a need for ongoing training and support even for communication partners who use sign regularly.