The choice of pediatric metabolic syndrome (MetS) definition influences prevalence estimates, but further implications, especially on the association with socioeconomic status (SES), are not well-known. This hampers a synthesis of the evidence to help guide the relevant stakeholders. For this reason, we aim to assess the impact of alternative definitions on the prevalence of MetS, the children that are identified, and the association between SES and MetS.Data were used from the Lifelines Cohort Study, a prospective multigenerational cohort in the Netherlands. At baseline 9,754 children participated, of which 5,085 (52.1\ were included in the longitudinal analyses. We computed the prevalence of MetS according to five published definitions and measured the observed positive agreement between pairs of definitions, indicating the proportion of agreement across the average number of MetS cases. Logistic regression was used to assess the association between SES and MetS. All models were adjusted for age and sex; the longitudinal models were also adjusted for baseline MetS status.The prevalence rates of MetS varied between definitions (0.7-3.0\, but positive agreement between MetS definitions was generally fair to good ranging from 0.34 (95\CI) 0.28; 0.41) to 0.66 (95\.58; 0.75) at baseline. At both assessments, we found an inverse association between baseline SES and MetS, which ranged from 0.81 (95\.70; 0.93) to 0.92 (95\.86; 0.98) per definition in the longitudinal analyses with a mean follow-up (SD) of 3.0 (0.75) years.Alternative definitions of MetS lead to differing prevalence estimates, and they agreed on 50\ regardless of which definition was used we concluded low SES was a risk factor for developing MetS.Evidence regarding different definitions of metabolic syndrome in children can be combined because the agreement among definitions is generally fair to good.As low socioeconomic status is a consistent risk factor for developing metabolic syndrome, preventive interventions should preferentially target children from low socioeconomic backgrounds.