In higher education, the desire to internationalize has created demands for an internationalized academia to use English increasingly in teaching outside the English native-speaking world. Given this situation, perhaps other criteria for measuring successful communication should be considered than that of the native-speaking minority. With lecturers whose native language is not English increasingly teaching their subjects through English, there is a growing need to develop adequate measures for this purpose and situation as the current normative standards are no longer tenable. Establishing adequate measures for this purpose and situation are relevant to institutions facing the challenge of providing EMI courses and programs while ensuring credible quality control. In order to determine what criteria might be adequate for assessing spoken professional English in an international context, this study investigates self-assessments of professional language in relation to language ideologies. The study involves English-medium instruction (EMI) in the field of engineering and takes place at a Finnish university. Using a mixed-methods approach, the study employed an explorative strategy that involved a concurrent design. The two methods were used in parallel and the results integrated at the interpretation phrase. This approach provides a general picture through micro- and macro-level analyses: the self-perceptions of EMI lecturers (i.e. qualitative) and their students perceptions of English in lectures (i.e. quantitative). The investigation employs a bottom-up approach, and is primarily qualitative. The findings are based on authentic data: video-recorded interviews and lectures, their transcriptions, and a questionnaire. The findings show that EMI lecturers have two basic representations of their English: A) when they compare their English to native-like targets, they find fault with their English, and B) when they think of themselves in their normal work environment, they see their English as working rather well. Certain language ideologies induced type A discourse, including standard language and NS language ideologies, and others induced type B discourse, such as English-as-a-global-language ideologies. The results from the student questionnaire also support interpretation B. Since meaningful testing should reflect the target situation, what my informants say in the type B discourse is relevant to developing assessment criteria. Their views to Common European Framework of Reference for Languages (CEFR) scales are also extremely useful in pointing the way towards the central elements upon which relevant assessments for professional English in an international environment should be based. The conclusions indicate a comprehensibility goal over native-likeness for assessing spoken professional English in an international context. The study outlines some criteria relevant for assessing spoken English for this purpose and situation.