Anti-Müllerian hormone (AMH) is a glycoprotein significant for sex differentiation during embryogenesis. In women, it is produced by the granulosa cells of ovarian follicles. Since serum concentrations of AMH correlate with the number of antral follicles and fluctuate the least during the menstrual cycle compared to other hormones, it is currently used as a biomarker for ovarian reserve. The exact role of AMH in childhood and whether fertility in girls can be assessed at an early age remains an ongoing area of research. Studies that have attempted to establish reference values in prepuberty and puberty show that the first increase in AMH concentration occurs in the postnatal period, followed by another increase before the onset of puberty. Entering puberty leads to a slight decline, followed by another increase and stabilization of concentrations until around the age of twenty-five, when concentrations begin to decline. Although most studies agree on the fluctuations in AMH concentrations during childhood, the specific values and exact ages at which each transition occurs do not always match. The significance of extremely low or high concentrations in childhood could be useful in assessing fertility in certain pathological conditions such as precocious puberty, Turner syndrome, polycystic ovary syndrome, but also in early assessment of premature ovarian insufficiency. However, measuring AMH values with different immunoassays, the insufficiently understood physiology of AMH, and the potential influence of currently unknown factors on serum AMH concentrations make it challenging to determine reference values. Further research and standardization of AMH measurement tests are needed for AMH to be used in clinical practice during childhood in the future.