The etiology of posttransplant erythrocytosis (PTE) remains unclear, and the most frequently suggested causative factors are still a matter of controversy. We aimed to investigate serum-soluble stem cell factor (sSCF) along with serum erythropoietin (EPO) levels in renal transplant recipients (RTRs) with PTE. Thirteen RTRs with PTE, 42 RTRs without PTE, and 42 healthy controls were included. Serum sSCF and EPO levels were determined using an enzyme-linked immunosorbent assay kit. Expected and observed/expected EPO levels were calculated. Serum sSCF levels and observed/expected EPO were significantly higher in RTRs with PTE than both RTRs without PTE and controls. In RTRs with PTE, sSCF level was significantly correlated with hematocrit and observed/expected EPO, respectively. Significant correlation was also observed between hematocrit level and observed/expected EPO in RTRs with PTE. Increased sSCF level and inadequate suppression of EPO production seem to have a role in the pathogenesis of PTE.