Producing accessible information for people with intellectual disabilities has been seen as a priority for the past 20 years. Easy‐read resources are now widely available and several guidelines have been produced to support their development. However, little is known about the effectiveness of easy‐read resources and the specific components that make it effective. A systematic review of the literature in electronic databases (Medline, Embase, BNI, CINAHL, HMIC, PsycINFO, ERIC, PubMed, and Cochrane Library) conducted between November 2013 and January 2014 yielded 11 publications that attempted to evaluate the impact of easy‐read resources. The large variation in methodology among studies prevented a direct comparison of results; however, there were mixed findings concerning the impact of adding illustrations to written text on comprehension. A reader's level of familiarity with symbols emerged as an important factor, particularly with more abstract symbol systems that require some learning. Photographs and illustrations were generally found to be helpful, although it was acknowledged that these can be confusing and clear explanations are needed to ensure the correct message is conveyed. The format and level of difficulty of the text played an important role in the overall accessibility of information and particular linguistic features were associated with increased understanding. The methodological limitations of these studies were also considered and used to inform recommendations for future research. More attention needs to be focused on evaluating and distributing easy‐read information, as well as producing it.