This volume contains the proceedings of the Eighth Workshop on Model-Based Testing (MBT 2013), which was held on March 17, 2013 in Rome, Italy, as a satellite event of the European Joint Conferences on Theory and Practice of Software, ETAPS 2013. The workshop is devoted to model-based testing of both software and hardware. Model-based testing uses models describing the required behavior of the system under consideration to guide such efforts as test selection and test results evaluation. Testing validates the real system behavior against models and checks that the implementation conforms to them, but is capable also to find errors in the models themselves. The first MBT workshop was held in 2004, in Barcelona. At that time MBT already had become a hot topic, but the MBT workshop was the first event devoted mostly to this domain. Since that time the area has generated enormous scientific interest, and today there are several specialized workshops and more broad conferences on software and hardware design and quality assurance covering model based testing. MBT has become one of the most powerful system analysis tools, one of the latest cutting-edge topics related is applying MBT in security analysis and testing. MBT workshop tries to keep up with current trends.