An Alzheimer’s Association workgroup published criteria for the diagnosis of Alzheimer’s disease (AD) that included a six-stage (1-6) clinical classification schema. Stages 1 (asymptomatic stage) and 3-6 (mild cognitive impairment and dementia stages) are clinically familiar. However, Stage 2 does not have an existing clinical analogue; it consists of subtle cognitive or behavioral declines that do not rise to the level of impairment. To ensure research consistency and accurate operationalization, we need consensus on the most appropriate nomenclature and measurement strategies to define Stage 2 cognitive decline. We present results of a Delphi consensus study on this topic. A steering committee of 15 members identified 105 experts on Stage 2 cognitive decline. 61 agreed to participate in a Delphi consensus study via three rounds of survey regarding the most appropriate nomenclature and operational criteria for defining Stage 2 cognitive decline in clinical trials. Participants stated their preferences among 16 potential terms for Stage 2 cognitive decline (e.g., objective subtle cognitive decline, transitional cognitive decline, subtle cognitive impairment). Additionally, they evaluated the appropriateness of 11 different operational approaches for Stage 2 cognitive decline. We defined consensus by 75% agreement. Consensus was reached for the term objective subtle cognitive decline. Similarly, there was consensus that cognitive screeners, interview-based measures, and cognitive intraindividual variability scores are inappropriate for defining objective subtle cognitive decline. While there was not consensus in favor of any operational approaches for defining objective subtle cognitive decline, there was a preference for single-assessment neuropsychological test approaches (e.g., pattern of low scores on a cognitive test battery). Objective subtle cognitive decline is the preferred term to describe objective decline in cognition that does not rise to the level of impairment. Further, there was consensus that cognitive screeners and interview-based measures lacked the sensitivity to identify objective subtle cognitive decline. However, more empirical research seems needed to identify the strongest methods for operationalizing objective subtle cognitive decline in clinical trials for AD and move towards consensus on measurement.