Background <p>The fermentation process, particularly when enhanced with plant extract additives, plays a crucial role in improving the quality of cigar tobacco leaves (CTLs). The development of novel functional fermentation additives and the analysis of their mechanisms of action are fundamental technological advancements in this field. This study concentrated on the development of extracts derived from spices and systematically examined their effects on the sensory quality, chemical components, and microbial communities of CTLs. </p> Results <p>The four spice extracts contain various active ingredients, such as cinnamic aldehyde and flavonoids. The addition of these spice extracts resulted in a reduction of nicotine and total nitrogen levels while increasing the contents of total sugar and reducing sugar in CTLs. Notably, the K/Cl ratio in the CTLs fermented with spice extracts exhibited an increase of 53–60%. In addition, the total amount of aroma substances in CTLs increased, and the contents of 3-hydroxy-5,6-epoxy-β-ionol, nerolidol, and other representative aroma components increased. The addition of spice extracts also contributed to a greater diversity within the fungal community. Correlation analysis revealed that microorganisms such as <i>Corynebacterium</i>, <i>Wallemia</i>, <i>Trametes</i>, and <i>Schizophyllum</i> were associated with the reduction of nicotine and the enhancement of typical aroma components. Furthermore, the CTLs fermented with spice extracts exhibited superior sensory attributes, characterized by a reduction in unpleasant odors and irritation and an enhancement in sweetness and pleasant aftertaste.</p> Conclusions <p>This study developed spice extracts as fermentation media to improve the quality of CTLs. It systematically analyzed the effects of these extracts, providing theoretical guidance for the advancement of additional fermentation media.</p> Graphical Abstract <p></p>