This article introduces an instrument for the indirect assessment of positive and negative affect, the Implicit Positive and Negative Affect Test (IPANAT). This test draws on participant ratings of the extent to which artificial words subjectively convey various emotions. Factor analyses of these ratings yielded two independent factors that can be interpreted as implicit positive and negative affect. The corresponding scales show adequate internal consistency, test-retest reliability, stability (Study 1), and construct validity (Study 2). Studies 3 and 4 demonstrate that the IPANAT also measures state variance. Finally, Study 5 provides criterion-based validity by demonstrating that correlations between implicit affect and explicit affect are higher under conditions of spontaneous responding than under conditions of reflective responding to explicit affect scales. The present findings suggest that the IPANAT is a reliable and valid measure with a straightforward application procedure.