Purpose: It is known that interpreter-mediated aphasia assessments may not provide the linguistic information that speech-language pathologists (SLPs) need to provide accurate diagnoses and determine treatment goals. The purpose of our study was to understand the perceptions of SLPs and interpreters who collaborate in a medical setting and to develop a checklist to categorize and quantify the errors interpreters make. Interpreter training may lead to unintentional errors that impact the information the SLP gains from the assessment session. Method: In Phase 1 of the study, 38 hospital SLPs and 26 interpreters responded to survey questions about their experiences working with the other discipline. In Phase 2, eight Spanish-speaking interpreters and two Spanish-speaking participants with fluent aphasia took part in a standardized interpreter-mediated aphasia assessment. A bilingual SLP and a Spanish-speaking interpreter analyzed and coded the assessments for errors in the interpreters’ behaviors. Results: Results from the survey demonstrated that both SLPs and interpreters would like the interpreters to have more education regarding the diagnosis of aphasia and an understanding of the SLP's goals during an aphasia assessment. A lack of time was considered the primary hindrance to educating interpreters during an evaluation session. The checklist included interpreter behaviors that could significantly impact the SLP’s ability to diagnose aphasia: omission of speech/language information, meaning errors, and cueing. Positive behaviors noted were calling attention to patient error and pointing out potential confusing items. Conclusions: Education for both disciplines will enhance the accuracy of interpreter-mediated aphasia assessments. A checklist tool with specific examples of errors may be useful in educating not only experienced interpreters and SLPs but also students in both disciplines.