Prior attempts at locating self-monitoring within general taxonomies of personality traits have largely proved unsuccessful. However, past research has typically neglected (a) the bidimensionality of the Self-Monitoring Scale and (b) the hierarchical nature of personality. The objective of this study was to test hypotheses that the two self-monitoring factors are located at the level of the metatraits. Using data from two large multi-informant samples, one community (Sample 1: N = 552, Mage = 51.26, 61% female; NPeers = 1,551, Mage = 48.61, 37% female) and one online (Sample 2: N = 3,726, Mage = 24.89, 59% female; NPeers = 17,868, Mage = 26.23, 64% female), confirmatory factor analysis was used to test the hypotheses. Results confirmed hypotheses that acquisitive self-monitoring would have a strong positive relation to metatrait Plasticity, whereas protective self-monitoring would have a moderate negative relation to metatrait Stability. In both samples, constraining the correlation between acquisitive self-monitoring and Plasticity to unity did not alter model fit indices, indicating that the two putatively distinct constructs are identical. Findings have wide-ranging implications, including integration of the construct of self-monitoring into the mainstream of personality research, as the latter moves toward the development of broad explanatory theories.