Research has demonstrated that implicit and explicit attitudes toward consensual nonmonogamy (CNM; sexually and/or emotionally nonexclusive romantic relationships) are less favorable than those toward monogamy. Although this general pattern of results is often reported, it is not clear to what extent this implicit difference reflects negative associations with CNM. To investigate this issue, the current study assessed 355 U.S. early emerging adults’ (89 men, 265 women, one gender nonconforming) implicit associations with CNM and monogamy using the Single-Target Implicit Association Test (ST-IAT). In addition, the convergent (using explicit measures), postdictive, and concurrent validity of the CNM ST-IAT was also investigated. The results revealed that although early emerging adults demonstrated a positive implicit association with monogamy (mean D score = 0.38), a neutral implicit association emerged for CNM (mean D score = 0.00). Additionally, young women and those without previous CNM experience demonstrated more negative implicit associations with CNM as compared to men and those with previous CNM experience. Finally, implicit associations with CNM predicted willingness to allow one’s partner to participate in CNM, but not one’s own interest in CNM. These results support previous research suggesting that a disparity in attitudes toward CNM and monogamy exists and provides further clarification reflecting positive implicit associations with monogamy and neutral associations with CNM. These results also confirm that monogamous relationships continue to be upheld as the ideal relationship structure in the U.S. and that educators/practitioners should work to reduce negative implicit bias toward CNM in an attempt to promote relationship equity.