Young people neither in employment nor in education or training (NEET) are at risk of long-term exclusion and poorer wellbeing. Besides individual costs NEET has a significant social and economic costs for the society. Using register data on Finnish birth cohorts born in 1987–1992, we compared the risk of being NEET at ages 21–27 between those born with very low birth weight (VLBW, <1500 g), low birth weight (LBW, 1500–2499 g), and normal birth weight (NBW). We further studied whether the effect of birth weight varies by maternal education. Poisson regression with sibling fixed-effects was used to reduce the confounding bias caused by unobserved family background factors. Results showed that LBW was related with an incidence rate ratio (IRR) of 1.27 (95 % CI 1.17–1.38) and VLBW with an IRR of 2.04 (95 % CI 1.69–2.47) to NEET status, compared to NBW. The associations between birth weight and NEET status did not vary by maternal education. Findings indicate that those born with LBW and especially VLBW are more likely to be NEET during young adulthood, demonstrating that perinatal health also matters for more disadvantaged socioeconomic outcomes. These adverse effects are not buffered by resources related to maternal education.