One new species of eriophyoid mite is described from Iceland and new records of three species from Iceland are presented. Aceria reykjaviki sp. nov., collected from Alpine Mouse-ear Chickweed Cerastium alpinum L., was described as new for science. Aceria thomasi (Nalepa), Aculops thymi (Nalepa), and Aculus tetanothrix (Nalepa) were recorded for the first time in Iceland. Aculops thymi was recorded for the first time as infesting Thymus praecox Opiz. As former descriptions are deficient, supplementary descriptions of females and males are provided for all three species. Nymphs are characterized for A. thomasi and A. tetanothrix.