Background: Acute coronary syndromes present clinically as a consequence of plaque rupture and thrombosis possibly related to altered homeostasis of thrombogenic factors. It is speculated that this vulnerability in adults should be predictable from blood levels of thrombogenic biomarkers in children and adolescents. This study aims to examine the determinants and blood levels of lipoprotein(a) [Lp(a)], fibrinogen (FBG) and plasminogen activator inhibitor-1 (PAI-1) in healthy adolescents stratified according to age group, gender and body mass. Methods: A total of 774 (316 males 458 females) healthy adolescent Arab subjects aged 10–19 years and attending secondary schools in Kuwait were interviewed by a validated questionnaire for variables relating to socio-demographic variables, diet and physical activity. They also had anthropometry, BP measurement and determination of fasting blood levels of Lp(a), low density lipoprotein (LDL)-cholesterol, apolipoprotein (apo) B, PAI-1 activity and FBG. Results: The median (interquartile range, IQR) plasma levels of PAI-1 activity, FBG, Lp(a) and apoB were respectively 1.59 (0.58–3.78) U/mL, 296 (190–417) mg/dL, 10.0 (4.8–21.0) mg/dL and 0.72 (0.60–0.85) g/L. Boys had significantly higher PAI-1, FBG and apoB concentrations than the girls, although Lp(a) levels were greater in the latter. The overweight and obese subjects tended to have higher levels of LDL, apoB, FBG and PAI-1 but not Lp(a). Furthermore, the younger adolescent males and females (age <14 years) consistently had higher FBG levels than the older ones (age >14 years). Lp(a) and PAI-1 levels did not appear significantly influenced by this age stratification. Bivariate and multivariate analyses with adjustment for putative body mass index (BMI) confounders indicated that the independent determinants of these biomarkers were (i) Lp(a): apoB, gender; (ii) PAI-1: BMI, apoB, diet; (iii) FBG: BMI, gender, age, family income; and (iv) apoB: BMI, gender and PAI-1. Conclusions: The blood levels of the prothrombotic biomarkers ;ibLp(a), PAI-1, and FBG;ic in healthy Kuwaiti adolescent subjects are variably influenced by age, gender, body mass and socio-demographic factors.