The differentiation of personality by intelligence hypothesis suggests that there will be greater individual differences in personality traits for those individuals who are more intelligent. Conversely, less intelligent individuals will be more similar to each other in their personality traits. The hypothesis was tested with a large sample of managerial job candidates who completed an omnibus personality measure with 16 scales and five intelligence measures (used to generate an intelligence "g"-factor). Based on the "g"-factor composite, the sample was split using the median to conduct factor analyses within each half. A five-factor model was tested for both the lower and higher intelligence halves and were found to have configural invariance but not metric or scalar invariance. In general, the results provide little support for the differentiation hypothesis as there was no clear and consistent pattern of lower inter-scale correlations for the more intelligent individuals.