Latar belakang. Peran copeptin pada pneumonia masih merupakan kontroversi. Tujuan. Mengetahui hubungan antara kadar copeptin serum dengan derajat pneumonia pada anak balita. Metode. Kami melakukan penelitian secara cross sectional pada anak dengan kriteria pneumonia menurut kriteria WHO dan radiologis. Sampel diambil secara consecutive sampling dan dilakukan pemeriksaan kadar copeptin serum. Orang tua atau wali subjek penelitian diminta menandatangani inform consent. Penelitian ini dilaksanakan dibawah persetujuan Komite Etik. Hasil. Didapatkan hasil 38 anak yang terdiri dari 25 laki-laki dan 13 perempuan dengan rerata umur 14,26 (SD 13,544) bulan. Rerata kadar copeptin serum 13.868 ng/mL. Didapatkan hubungan positf antara kadar copeptin serum dengan derajat pneumonia. Background. There has been controversy in the role of serum copeptin level in pneumonia. Objective. To assess a correlation between serum copeptin with severity of pneumonia in children under five years old. Method. We conducted a cross-sectional study in children with pneumonia. Diagnosis was based on WHO criteria plus chest x ray findings. We recruited sample consecutively and examined serum copeptin level in children who met the criteria as sudy participants. Informed consents were obtained from parents or guardians. This study was approved by ethical comitte. Results. Subjects were 38 children, consist of 25 boys and 13 girls with an average age 14.26 (SD 13.544) months. Mean serum copeptin levelwas 13,868 ng/mL. We found a positive correlation between serum copeptin levelwith the severity of pneumonia. (r=0.781 and p<0.0001) Conclusion. There is a significant and strong correlation between levels of serum copeptin with the degree of pneumonia. Sari Pediatri 2015;17(4):292-6.