Kabupaten Simalungun terdapat 32 Kecamatan, 27 Kelurahan dan 386 Desa dengan Jumlah Penduduk 1.037.951 jiwa sesuai dengan Data Agregat Kependudukan Semester II Tahun 2020
| NO | KECAMATAN | LAKI -LAKI | PEREMPUAN | JUMLAH |
| 1 | SIANTAR | 39.968 | 39.735 | 79.703 |
| 2 | GUNUNG MALELA | 23.492 | 23.188 | 46.680 |
| 3 | GUNUNG MALIGAS | 19.201 | 18.366 | 37.567 |
| 4 | PANEI | 15.779 | 16.155 | 31.934 |
| 5 | PANOMBEIAN PANEI | 14.006 | 13.891 | 27.897 |
| 6 | JORLANG HATARAN | 10.744 | 10.795 | 21.539 |
| 7 | RAYA KAHEAN | 11.879 | 11.811 | 23.690 |
| 8 | BOSAR MALIGAS | 23.912 | 23.434 | 47.346 |
| 9 | SIDAMANIK | 16.838 | 17.109 | 33.947 |
| 10 | PAMATANG SIDAMANIK | 10.108 | 10.018 | 20.126 |
| 11 | TANAH JAWA | 28.118 | 28.048 | 56.166 |
| 12 | HATONDUHAN | 13.525 | 13.578 | 27.103 |
| 13 | DOLOK PANRIBUAN | 11.318 | 11.295 | 22.613 |
| 14 | PURBA | 14.137 | 13.781 | 27.918 |
| 15 | HARANGGAOL HORISON | 3.526 | 3.534 | 7.060 |
| 16 | GIRSANG SIPANGAN BOLON | 8.965 | 9.092 | 18.057 |
| 17 | DOLOK BATU NANGGAR | 23.485 | 22.840 | 46.325 |
| 18 | HUTA BAYU RAJA | 17.864 | 18.163 | 36.027 |
| 19 | JAWA MARAJA BAH JAMBI | 11.695 | 11.958 | 23.653 |
| 20 | DOLOK PARDAMEAN | 8.104 | 7.835 | 15.939 |
| 21 | PEMATANG BANDAR | 20.162 | 19.991 | 40.153 |
| 22 | BANDAR HULUAN | 15.022 | 14.907 | 29.929 |
| 23 | BANDAR | 40.372 | 39.723 | 80.095 |
| 24 | BANDAR MASILAM | 15.141 | 15.052 | 30.193 |
| 25 | SILIMAKUTA | 8.905 | 8.847 | 17.752 |
| 26 | DOLOK SILAU | 9.010 | 8.980 | 17.990 |
| 27 | SILOU KAHEAN | 10.126 | 10.080 | 20.206 |
| 28 | TAPIAN DOLOK | 23.326 | 22.463 | 45.789 |
| 29 | RAYA | 15.567 | 15.808 | 31.375 |
| 30 | UJUNG PADANG | 23.113 | 22.654 | 45.767 |
| 31 | PAMATANG SILIMAHUTA | 6.832 | 6.854 | 13.686 |
| 32 | DOLOG MASAGAL | 6.922 | 6.804 | 13.726 |
| JUMLAH | 521.162 | 516.789 | 1.037.951 |
