Purpose: The current study used a case review diagnostic assessment task to examine the diagnostic decisions speech-language pathologists (SLPs) working in the United States made after reviewing child language cases. Method: Fourteen SLPs were given 5 case studies that presented either congruent or incongruent results between standardized testing and informal measures. After reviewing the assessment data, SLPs were asked to make a diagnostic decision. Results: Unanimous consensus regarding diagnostic decisions was found when the assessment data were congruent. When the data were incongruent, unanimous consensus was not achieved. Standardized testing seemed to guide the diagnostic decision. This pattern of reliance on standardized testing was evident even when 80% of SLPs reviewed informal language data. In 97% of cases, a standardized test was used to guide clinical decision making. Conclusion: Three patterns of clinical decision making in child language assessment emerged: (a) use of both standardized testing and informal measures, (b) a reported concern tool as a 1st step in the process, and (c) standardized testing as the most influential data for guiding diagnostic decisions. Although this study provides initial evidence regarding the process of diagnostic decision making, future studies should examine decision making in real time to further validate the implicit rules used during decision making.