Collembola of the species Folsomia candida were exposed towards copper oxide nanoparticles or copper chloride in a laboratory test. Springtails were exposed in artificial test soils either containing kaolin or Montmorillonite K10 as clay fraction. Size of clay fraction was either 19 or 30% of total mass. The survival, reproduction, dry weight and Cu bioaccumulation were assessed in a 28-day reproduction test. Metallothionein levels, Catalase activity, moulting frequency and Cu content of the exuviae were assessed after a 6-day exposure. Results indicated toxic effetcs on physiological and molecular endpoints and a non-linear dose-response relationship for copper oxide nanoparticles when applied in montmorillonite soil, but not in kaolin soil.