Herein, SnS₂ particles with two different morphologies are synthesized using a template‐free one‐step hydrothermal method. Flower‐ and plate‐like SnS₂ are obtained using different solvents, ethyl alcohol, and deionized water, respectively, under the same synthesis conditions. The flower‐like SnS₂ had a larger surface area and higher concentration of sulfur vacancies than plate‐like SnS₂. The effects of the specific surface area and the number of sulfur vacancies in the gas‐sensing materials are studied using the gas‐sensing characteristics of SnS₂ in the two morphologies. The gas sensitivities at 25 °C under 1 ppm NO₂ are 73.5 and 129.5 for flower‐ and plate‐like SnS₂, respectively. Both the flower‐ and plate‐like SnS₂ gas sensors exhibited good gas selectivity for NO₂ against SO₂, CO, and NH₃ at 25 °C. The response and recovery times are 540 and 1407 s for the flower‐like SnS₂ and 214 and 18 s for the plate‐like SnS₂, respectively. It is confirmed that a large specific surface area and the number of sulfur vacancies adversely affected the response and recovery times. Therefore, the plate‐like gas sensor is expected to be a good candidate for NO₂ gas‐sensing applications at 27 °C.