In this study, we tried to describe the variations of tense(present, past and retrospective) and modality (conjecture and intention) morphemes in Korean dialects. A lot of dialectal variants can be seen in the description, some of which are relics of middle Korean, and the others are the results of their own changes in form and meaning. Some dialects show the peculiar variants one of which is ‘-łk$^$h/ł’ of Cheju duakect that has no etymological relation with inland form, ‘-kess-’. In spite of the variations, however, all Korean dialects basically have the same systems of tense and modality, for which every speaker of Korean dialects has little difficulty in understanding time expressions and psychological attitudes of others.