Background Children born very preterm (VP <32 weeks gestation) and/or with very low birth weight (VBLW <1500 g; subsequently VP/VLBW) have been previously reported to have more cognitive impairment and specific executive functioning problems than term children; however, it remains unclear whether these problems persist into adulthood. This study aimed to examine general intelligence (IQ) and executive functioning (EF) of adults born VP/VLBW in comparison to term controls. Additionally, the effects of smallness for gestational age (SGA) and family socioeconomic status (SES) at birth were investigated. Methods The Bavarian Longitudinal Study is a geographically defined prospective cohort study of neonatal at-risk children born in 1985/86 in Southern Germany. A total of 217 VP/VLBW and 197 controls completed the battery of IQ and EF tests at 26 years of age. Results VP/VLBW adults scored significantly lower than controls in IQ and EF. There was a 1.16 standard deviation (SD) unit difference between the VP/VLBW and controls in Full-Scale IQ. VP/VLBW adults were found to have general and multiple cognitive problems rather than specific deficits in EF. SGA was not a significant predictor of cognitive impairment. Family SES had a significant impact on general intelligence in both VP/VLBW and term controls. The SES effects amounted to 1.13 SD units between individuals born into high versus low SES. Conclusions No narrowing of cognitive deficits between VP/VLBW and term control adults to previous childhood assessments at 6 years of age was found. VP/VLBW adults do not outgrow their cognitive problems despite many receiving special educational support in childhood. Low family SES at birth has similar additive adverse effects on cognitive performance in VP/VLBW and term offspring.