This study first describes the uses of the Sakha and Tyvan WH-question suffixes, and then provides a contrastive analysis of the WH-question suffixes of the two cognate languages. The Tyvan WH-question suffix has a wider range of usage than the equivalent Sakha suffix. The appearance of the Tyvan WH-question suffix in non-existential and presumptive sentences is particularly interesting because they contain no WH words. The function of the Tyvan WH-question suffix in non-existential and presumptive sentences should be explained by the concept of egophoricity. In non-existential sentences, the WH-question suffix describes the speaker’s mental status in the form of assertions and in questions the hearer’s mental status. In presumptive sentences, it expresses an inference based on the speaker’s feelings, memories, or observations. In conclusion, the occurrence of the Tyvan WH-question suffix is a pragmatically conditioned element rather than a grammatically required question marker.