The chemical composition of six essential oils (EOs) of Thymus serrulatus and Thymus schimperi from six localities in Ethiopia, namely Ofla, Alamata, Yilmana Densa, Tarmaber, Butajira and Bale was determined. The in vivo hepatoprotective potential of three of the EOs was evaluated. GC-MS and NMR were used to determine chemical composition and GC-FID to quantify the main compounds. The number of EO components ranged from 17 to 41. The EOs were of two chemotypes with either thymol (Ofla, Alamata, Tarmaber and Bale) or carvacrol (Yilmana Densa and Butajira) being the main compound. Hepatoprotection of EOs was tested against paracetamol-induced hepatotoxicity in Wistar albino rats. Hepatoprotective properties of the oils were demonstrated by reduced serum levels of hepatic marker enzymes (AST, ALT and ALP) and normal hepatocytes structure. The most effective one was the thymol type EO from Alamata.