Telomeres are repetitive DNA sequences at the ends of chromatids that shorten following each cell replication. Once telomeres reach a critical length, DNA defense mechanisms can direct cells to either a state of arrest (senescence) or apoptosis. Stress induced by adversity is a probable cause of accelerated telomere shortening from an early age. However, few studies have examined the association between stress and telomere length in children, and it remains unclear whether young individuals may show signs of cellular aging early in life. Our aim was to examine whether adversity in childhood is associated with shortening of telomere length. We conducted a systematic review of studies that investigated the association between stress and telomere length in children from 3 to 15 years of age. Eleven studies met our selection criteria. We concluded that adversity in childhood (such as violence, low socioeconomic status, maternal depression, family disruption, and institutionalization) have an impact on telomere length. This suggests that exposed individuals show signs of accelerated erosion of telomeric ends from an early age. We discuss whether telomere shortening is related to negative health outcomes later in life or could be a biomarker predicting health outcomes. We believe that further large-scale longitudinal studies that repeatedly monitor telomere length are very important for providing a better assessment of telomere trajectory in psychologically stressed children. This will verify the extent to which adversity impacts upon the biological development of cell aging in childhood.