Thiocyanate-containing protic ionic liquids (PILs) have previously proven to be useful reagents for conducting diverse chemical transformations. A fundamentally new concept of multi-purpose application of these PILs opens up new opportunities in organic synthesis. However, their safety has not been thoroughly assessed so far. In this work, we carried out a systematic investigation of cytotoxicity of a series of synthetically valuable thiocyanate-containing PILs towards normal human dermal fibroblasts (DF-1) and human embryonic kidney cells (HEK293T). In particular, the impact of anion on the cytotoxicity was studied for dual-purpose triethylamine-based PILs. The study of cellular damage markers yielded additional insights into the mechanisms of PILs’ cytotoxicity. © 2025 Elsevier B.V., All rights reserved.