Cohesive Zone Models (CZM) are widely used for modeling bonded joints. The main difficulty concerning the use of CZM is the obtention of the interface cohesive law. To measure the cohesive law of bonded joints, experimental methods have been developed which are tedious and expensive because they require the use of additional measurement techniques in addition to the basic test outputs (load and displacement) to measure the J-integral and the crack opening displacement, essential parameters that obtain the cohesive law. In this work, a method is presented to obtain the cohesive law directly from the load-displacement curve of a DCB test. The method combines a model based on Dugdale's condition with an inverse method. The method is compared to the measurements from other authors who used the aforementioned more costly existing methods, and a good agreement between them is obtained. The method presented reduces the instrumentation needed during the test and it is very useful when testing under extreme conditions requiring the use of environmental chambers.