In many parts of the world, speech-language pathologists (SLPs) are frequently called upon to assess aphasia in bilingual speakers, or in speakers of languages of which they have little or no knowledge. One of the strategies that SLPs employ in these situations is to involve an interpreter in the assessment process. Three authentic interpreter-mediated aphasia assessments were analysed for the present study, which aimed to determine the degree to which the content validity of the individual tests was compromised in the process of their administration through an interpreter. Findings reveal that content validity was frequently weakened either at the point of administration of the test or at the point at which responses were reported back by the interpreter to the SLP. Based on these findings, it is argued that the conduct of interpreter-mediated aphasia assessments needs to be fundamentally re-thought to take account of the limitations inherent in the interpreting process. To this end, this study presents a number of practical recommendations for the involvement of interpreters in aphasia assessments, with a view to making optimal use of existing assessment materials and enhancing the quality of diagnostic information to emerge from such clinical sessions.