Purpose The purpose of this study was to examine confidence levels and identify predictors of increased confidence of school-based speech-language pathologists (SLPs) relative to different aspects of the augmentative and alternative communication (AAC) assessment process. Method Surveys were completed by 272 school-based SLPs. Questions were designed to capture demographic information and confidence in areas of assessment such as student capabilities, participation, and feature matching. Results There were variable levels of confidence across aspects of assessment. Respondents were less confident in tasks related to assessing students with severe physical impairments and incorporating aspects related to cultural and linguistic diversity in their assessment. SLPs were more confident assessing student participation and unaided communication. Additionally, respondents had less confidence in matching the features of high-tech speech-generating devices to their students. Self-identification as an AAC specialist, years of experience, percentage of caseload of students with complex communication needs, and length of longest continuing education experiences all contributed to predicting confidence in most areas of assessment. However, years of experience did not contribute to predicting confidence in feature matching. Conclusions Results from this study acknowledge that SLPs are likely to have varied degrees of confidence in aspects of assessment related to preparation, clinical experience, and self-identification of specialty. Findings from this study support increasing training opportunities in AAC assessment. As specialization was the strongest predictor of confidence, further research should investigate the characteristics and preparation of self-identified AAC specialists. This is an important first step in pinpointing ways to increase confidence in school-based SLPs.