Introduction: Children with chronic kidney disease (CKD) and receiving peritoneal dialysis (PD) have disorders of mineral metabolism that impact their growth, survival and cardiovascular functions. New molecular markers offer a better understanding of the pathophysiology of this disease. Objective: To characterize some components of mineral metabolism, with emphasis on FGF23/Klotho and cardiovascular functions (CV) of these patients. Patients and Method: Prospective observational cohort study. Exclusion criteria: serum 25 (OH) vitamin D < 20 ng/ml, peritonitis within the last two months and active nephrotic syndrome. Calcemia, phosphemia, parathyroid hormone (PTH), 25 (OH) vitD3, 1.25 (OH) vitD3, FGF23 and Klotho in plasma were measured. FGF23 and Klotho were quantifed in healthy children as a control group. Echocardiography was performed calculating the left ventricular mass index (LVMI). Descriptive statistics analysis, Pearson correlation coeffcient for association among variables and multivariate analysis were conducted. Results: 33 patients, 16 males, aged between 1.2 and 13.4 years were included. Age of onset for PD: 7.3 ± 5.0 years, time receiving PD: 13.5 ± 14.5 months. The plasma concentration of 25 (OH) vitD3 was 34.2 ± 6.3 pg/ml. Calcemia and phosphemia values were 9.8 ± 0.71 and 5.4 ± 1.0 mg/dl respectively. PTH was 333 ± 287 pg/ml. FGF23 in plasma was 225.7 ± 354.3 pg/ml and Klotho 131.6 ± 72 pg/ml, and in the controls (n = 16), it was 11.9 ± 7.2 pg/ml and 320 ± 119 pg/ml, respectively. The residual and total dose of dialysis (KtV) was 1.6 ± 1.3 and 2.9 ± 1.6, respectively. FGF23 levels signifcantly correlated with calcium (p < 0.001, r = 0.85), and inversely with residual KtV, showing no relationship with phosphemia. Klotho level correlated negatively with residual KtV and also, it showed a negative association with chronological age and age at onset of PD. LVMI > 38 g/m2 was confrmed in 20/28 patients. Conclusions: The values of FGF23, and PTH are elevated in children with CKD on PD. Klotho levels in CKD patients are lower than control children. A strong association of calcemia with FGF23 and PTH is reported. Residual renal function is inversely associated with FGF23 and Klotho. A high incidence of left ventricular hypertrophy was found evidencing a cardiovascular compromise in these patients.