Hypercalcemia is a potential adverse effect of calcium-containing ion exchange resins, often used in the treatment and prevention of hyperkalemia in chronic kidney disease (CKD). We describe a series of seven outpatients with moderate CKD (mean glomerular filtration rate estimated with the CKD-EPI formula 41.29±10.83mL/min/1.73m2), presenting mild hypercalcemia in relation to the treatment with calcium polystyrene sulfonate. Serum calcium increased a mean of 0.91±0.46mg/dL, with a mean concomitant decrease of serum intact parathormone (iPTH) of 52.24±49.29ng/dL. After treatment withdrawal or dose reduction, we observed a recovery of serum calcium and iPTH values. Treatment with calcic potassium binders should be included in the differential diagnosis of hypercalcemia in patients with moderate CKD.