To the first declension belongs masculine nouns which ends with -s or -š in singular nominative. The case endings are given in following table:
| Nom. | Gen. | Dat. | Acc. | Loc. | Voc. | |
| sing. | -s, -š | -a | -am | -u | -ā | -s |
| plur. | -i | -u | -iem | -us | -os | -i |
The first declension nouns which ends with -tājs, -ājs, -ējs, -nieks or which are diminutives has no ending in singular vocative.
| Nominative | tēv-s | tēv-i |
| Genitive | tēv-a | tēv-u |
| Dative | tēv-am | tēv-iem |
| Accusative | tēv-u | tēv-us |
| Locative | tēv-ā | tēv-os |
| Vocative | tēv-s | tēv-i |