<p>Preterm and low birth weight infants are at heightened risk for psychological and behavioral problems, yet prior meta-analyses have narrowly examined specific abnormalities, limiting insight into the broader development of internalizing and externalizing symptoms. This meta-analysis aimed to address this gap by estimating the magnitude of these risks compared to full-term infants. Searches were conducted in five databases: Web of Science, Embase, Scopus, Cochrane Library, and PubMed. Fifty-six studies were identified, with symptoms assessed from childhood (0-9 years) through adolescence (10-18 years) and into adulthood. Findings showed that preterm infants and low-birth-weight infants as a whole are more likely to experience internalizing symptoms (such as anxiety or depression) and externalizing symptoms (such as impulsivity or aggression) than full-term infants, though this risk is neither uniform or absolute—the risk of internalizing symptoms among low-birth-weight infants is relatively modest. Additionally, there are several clear moderating factors influencing the intensity of these risks. Regionally, the association between both types of symptoms and preterm birth or low birth weight is most pronounced in European samples. In terms of developmental stages, internalizing behaviors are more prominent in adolescent populations, whereas the risk of externalizing symptoms is higher in children. Regarding the severity of preterm birth and low birth weight, the association between both symptoms and these conditions is strongest in samples of extremely preterm infants or those with extremely low birth weight. This study advances understanding of the risks of internalizing and externalizing symptoms in preterm or low-birth-weight infants across different developmental stages, while revealing the potential impacts of region, age, and the severity of risk factors in this context.</p>