The current longitudinal developmental study was designed to determine whether awareness of one’s own biases (the metacognitive self, MCS) emerges and develops during the developmental period known as emerging adulthood. To this end, we followed almost 400 undergraduate university students (18–23 years) over the first three years of their studies, capturing data at five time points. We observed a growth in MCS that we explain in terms of the cognitive and motivational processes characteristic of emerging adulthood. We also observed group differences in MCS development. Students who performed better on the MCS scale at the very beginning of the study tended to show a greater increase in the MCS than those who scored poorly. Emerging adulthood appears to be a very important period with respect to individual differences in becoming aware of one’s own biases