The Association of Language Centres in Higher Education in Spain (ACLES) and the Association of Academic Foreign Language Centres in Poland (SERMO) established the mutual recognition of their English language competence certificates (CertAcles and ACERT examinations) in 2017, on the basis of previously performed analyses of routine pre-exam and exam procedures, specifications and applied evaluation criteria. This paper represents a further step towards comparability by reporting the results of a quantitative and qualitative analysis of data from a summer examination session in 2018 carried out with Spanish and Polish students who took a commonly developed English exam combining the features of both certification systems. The exams were carried out at Universitat Politècnica de València (ACLES) and Poznan University of Technology (SERMO) and the data was collected by means of test scores, student and teacher questionnaires, and semi-structured interviews. The results obtained are encouraging and provide a strong basis for further collaboration between the certification systems. Furthermore, they give support to the mutual recognition of our certificates while encouraging similar studies with other non-commercial university accreditation frameworks. These initiatives are in line with the objectives of the Bologna Process, facilitating student and staff exchange between institutions within the European Higher Education Area.