Traditional metrics largely overlook grey literature. The new altmetrics introduced in 2010 as " new, online scholarly tools (that allow) to make new filters " (Altmetrics Manifesto), can include all kinds of scholarly output which makes them interesting for grey literature. The topic of our paper is the connection between altmetrics and grey literature. Do altmetrics offer new opportunities for the development and impact of grey literature? In particular, the paper explores how altmetrics could add value to grey literature, in particular how reference managers, repositories, academic search engines and social networks can produce altmetrics of dissertations, reports, conference papers etc. We explore, too, how new altmetric tools incorporate grey literature as source for impact assessment, and if they do. The discussion analyses the potential but also the limits of the actual application of altmetrics to grey literatures and highlights the importance of unique identifiers, above all the DOI. For the moment, grey literature missed the opportunity to get on board of the new movement. However, getting grey literature into the heart of the coming mainstream adoption of altmetrics is not only essential for the future of grey literature in open science but also for academic and institutional control of research output and societal impact. This can be a special mission for academic librarians.