Information regarding welfare consequences of early onset of Borderline Personality Disorder (BPD) is limited. This nationwide study aimed to estimate the educational and employment outcome and health care costs of patients with early-onset BPD compared with matched controls. All patients (< 19 years) with first diagnosis of BPD in the Danish Patient Register (NPR) during the period 1983–2015 were included. Health care costs and socioeconomic variables were extracted from national registers. A total of 171 patients was compared with 677 controls. At the age of 20 years, BPD patients had reached a statistically significantly lower educational level (including lower primary school grades) and employment status compared with the controls. When adjusting for the parents’ educational level, BPD patients were nearly 22 times more likely to be unemployed (OR = 21.7, 95% CI 11.9, 39.6), and nearly 15 times more likely to be on disability pension (OR = 14.8, 95% CI 5.0, 43.9) than controls. Furthermore, the total health care costs were more than 8 times higher in the BPD group. Early onset of BPD was associated with lower educational and vocational outcome and increased health care costs as early as at the age of 20 years. Even after controlling for parents’ lower socioeconomic status, the patients have poorer outcome than the control group. This underlines that initiatives to support patients in finishing school and secondary education is highly needed. Future prevention and early intervention programs should target patients with early-onset BPD and their families.