Numeracy, along with literacy and increasingly digital skills, is trumpeted in policies as a core skill for adults internationally. Yet, in policy advocacy and the “naming” of the field that is concerned with supporting the literacy and numeracy development of adults, numeracy is often a hidden face, a shadow following literacy. One needs to dig beneath the names of policies, education providers or professional associations to notice that they are also concerned with numeracy. Against this backdrop, this paper explores the views of expert informants from the adult literacy and numeracy practitioner community on the importance of numeracy development for adults and factors supporting or hindering adults’ participation in numeracy learning. The findings suggest that, notwithstanding the invisibility of numeracy in adult education, there are other barriers that limit greater participation and the realisation of the wide range of benefits that numeracy development can afford. The paper contributes to a greater understanding of the link between the environment for numeracy development and the range of benefits that can be accrued from participation in numeracy programmes.