Piaget's final stage of cognitive development, formal operations, involves reasoning skills that appear to relate to the traits of critical thinking. The current study was designed to assess whether a relationship exists between the level of cognitive development (as measured by the Lawson Classroom Test of Scientific Reasoning [Lawson CTSR]) and critical thinking (as measured by Assessment Technology Institute Critical Thinking Assessment-Entrance test [ATI-CTA-Ent]). This study explored the possible relationship between the level of cognitive development and the level of critical thinking exhibited by first semester nursing students seeking an Associate Degree (ADN). It also explored the relationship between specific subsets of cognitive development and critical thinking as a whole as well as between cognitive development and the distinct traits that characterize critical thinking. Furthermore, this project asked whether the level of general knowledge held by nursing students (as measured by Assessment Technology Institute Test of Essential Academic Skills [ATI-TEAS] is correlated with the level of cognitive development. All statistical analyses controlled for gender, age, and prior schooling. A sample of 190 first semester nursing students were administered the Lawson CSTR as a test of cognitive development, the ATI-CTA-Ent as a test of critical thinking and the ATI-TEAS as a test of general knowledge. In a hierarchical multiple regression analysis it was found that cognitive development accounted for 19.3% of the variance in critical thinking scores after controlling for gender, age and prior schooling. With multiple subscales on both the predictor (Lawson CTSR) and the criterion (ATI CIA) side, regression models noted ATI-Inference with the largest explained variance (21.15%) and the smallest for ATI Evaluation (9.36%). The covariates explained 9.6% and cognitive development explained an additional 33.6% of the variance in general knowledge. These findings suggest that measures of cognitive development are associated with measures of critical thinking ability.