Assessment of attitudes in inclusive education research is almost exclusively based on self-report scales. This may lead to overestimation of positive attitudes due to social desirability bias, and self-reported attitudes may not capture all relevant aspects of attitudes. Recently, Lüke and Grosche (2018a) proposed a new attitude test based on a single target variant of the Implicit Association Test. In their sample of pre-service teachers, Lüke and Grosche found self-reported attitudes toward inclusion to be related to socially desirable responding. In contrast, implicit attitudes, as measured by the Single Target Implicit Association Test (Inclusion STIAT), were unrelated to social desirability bias and neutral overall. Here, we attempted (1) to replicate these findings, and (2) to further test the discriminatory validity of the Inclusion ST-IAT using two samples expected to differ in their attitudes: pre-service teachers with a study program in primary education (PrE) and special education (SpE). In contrast to the findings by Lüke and Grosche (2018a), we found no evidence of a social desirability bias within self-reported attitudes, and implicit attitudes were positive overall. As expected, SpE pre-service teachers had more positive implicit attitudes than PrE pre-service teachers, which speaks to the validity of the Inclusion ST-IAT. We believe the Inclusion ST-IAT, in combination with self-reports, to be a promising tool in assessing attitudes and encourage further research in this field.