The histologic responses to varied parameters of 1,927-nm fractional thulium fiber laser treatment have not yet been sufficiently elucidated.This study sought to evaluate histologic changes immediately after 1,927-nm fractional thulium fiber laser session at various parameters.The dorsal skin of Yucatan mini-pig was treated with 1,927-nm fractional thulium fiber laser at varied parameters, with or without skin drying. The immediate histologic changes were evaluated to determine the effects of varying laser parameters on the width and the depth of treated zones.The increase in the level of pulse energy widened the area of epidermal changes in the low power level, but increased the dermal penetration depth in the high power level. As the pulse energy level increased, the increase in the power level under the given pulse energy level more evidently made dermal penetration deeper and the treatment area smaller. Skin drying did not show significant effects on epidermal changes, but evidently increased the depth of dermal denaturation under both high and low levels of pulse energy.These results may provide important information to establish treatment parameters of the 1,927-nm fractional thulium fiber laser for various skin conditions.