Non-profit organisations (NPOs) are one type of open data intermediaries connecting different actors in the open data ecosystem. They perform a number of activities, from requesting the government to open up the data to application development. Such activities can have an effect on open data usability barriers that other actors in the open data ecosystem encounter. The objective of this study is to systematically review the literature on the influence of NPOs' activities on the usability barriers for open data users in the open data ecosystem. The authors identified and analysed fourteen relevant papers. This study shows that NPOs conduct various activities that relate to different intermediary roles in the open data ecosystem, which in turn can affect certain usability barriers. Moreover, NPOs may perform different activities depending on the type of open data they work with. However, the connection between the activities and open data usability barriers for open data users cannot be clearly established from the selected articles, as most of them do not focus on establishing such a link. This review highlights a literature gap in relation to NPOs' activities and their effects on open data usability.