The Dunning-Kruger (DK) effect is a form of meta-ignorance of knowledge (Kruger & Dunning, "Journal of Personality and Social Psychology," 77(6), 121-1134, 1999) that has not been explored regarding mental illness public stigma. The current study examined the DK effect in this field by comparing participants' actual stigma (measured by a social distance scale) and their perceived stigma (measured by a self-rating scale compared to their peers). In addition, the effectiveness of two types of feedback on stigma reduction was explored. Undergraduate participants (N = 393) with low actual public stigma perceived their public stigma level to be higher than it was, while those with high actual public stigma perceived it to be lower, supporting the DK effect. Generalized feedback did not reduce public stigma, whereas personalized feedback reduced public stigma for participants with high public stigma. This study revealed the existence of meta-ignorance in the field of mental illness public stigma and the effectiveness of personalized feedback.