Abstract: To explore the effects and mechanisms of microbial fermentation on improving the aroma of tobacco extract and cut tobacco, a fungal strain ZC125 was isolated from cheese. Sensory evaluation verified that this strain produced a distinct fruity aroma, and it was identified as Galactomyces geotrichum based on morphological characteristics and ITS sequencing. A spore suspension of ZC125 was inoculated into YPD medium, tobacco extract, and cut tobacco substrate separately for fermentation. Gas chromatography-mass spectrometry (GC-MS) was used to analyze changes in volatile aroma compounds before and after fermentation, and sensory evaluation was conducted to assess the aroma profiles of the fermented products. Results showed that fermentation of ZC125 in YPD medium mainly produced fruity esters such as ethyl tiglate (relative content 22.72%). After fermentation of tobacco extract with ZC125, 18 new components were detected, including β-ionone, along with significant accumulation of woody-sweet aroma compounds such as 4-(3-hydroxy-1-butenyl)-3,5,5-trimethyl-2-cyclohexen-1-one (14.60%). In cut tobacco fermented with ZC125, 14 new components, including cedrol (4.52%), were formed, contributing to woody aroma notes. Phenethyl alcohol, a characteristic rose-like aroma compound, was detected in all fermented samples. Sensory evaluation indicated that ZC125 exhibited substrate-dependent differences in aroma profiles. Compared with the blank control (3.43), cigarettes supplemented with different fermented products showed significantly higher comprehensive sensory evaluation function (ƒ) values (6.67-8.04). Among them, the ZC125-tobacco extract fermentation group performed best in aroma quality (7.8) and comfort (7.5), while the ZC125-cut tobacco fermentation group was most prominent in aroma intensity (7.5) and sweetness (7.9). In conclusion, the fruity-aroma-producing G. geotrichum ZC125 isolated from cheese, significantly improved the aroma quality of tobacco, providing a promising microbial resource for cigarette flavor enhancement.