Emerging pollutants such as personal care products can reach the environment via effluents from wastewater treatment plants (WWTPs) and digested sludge. Only recently, the antidandruff agent and antimycotic climbazole was detected for the first time in a WWTP effluent with concentrations up to 0.5?μg/L. Climbazole acts as a C14-demethylase inhibitor (DMI) fungicide and thus has a high efficacy against fungi, but knowledge of its potential environmental impact is lacking. Therefore, the aim of the present study was to characterize climbazole's ecotoxicity by conducting standard biotests with organisms representing different trophic levels from the aquatic as well as the terrestrial ecosystems. It was found that the toxicity of climbazole is mostly similar to that of other DMI fungicides, whereas it proved to be particularly toxic to primary producers. The lowest median effective concentrations (EC50s) were determined for Lemna minor, at 0.013?mg/L (biomass yield), and Avena sativa, at 18.5?mg/kg soil dry weight (shoot biomass). Reduction of frond size in water lentils and shoot length in higher plants suggested an additional plant growth–retarding mode of action of climbazole. In addition, it was demonstrated here that for an ionizable compound such as climbazole, the soil pH can have a considerable influence on phytotoxicity. Environ Toxicol Chem 2013;32:2816–2825. ? 2013 SETAC