This study on the negative-order fractional space-time modified KdV (nfmKdV) equation provides a comprehensive analysis of how fractional differentials affect the dynamics of solitons in non-linear wave models. We are referring to introduces the nfmKdV equation, a significant extension of the traditional KdV equation, which is commonly used to model wave propagation in non-linear dispersive media. By developing both focusing and defocusing solutions and employing the Hirota technique to construct multisoliton solutions, the study opens new avenues for the exploration of fractional wave equations in diverse physical contexts. The use of fractional calculus, and specifically negative-order derivatives, enhances the model's ability to describe real-world phenomena with long-range interactions and memory effects, offering significant potential for future research in non-linear and fractional dynamics. This newly established result warrants further investigation determine its applicability to other non-linear fractional order models, and other existing methods may be employed to explore this new development. As the fractional order approaches one, the results align with well-established findings in the literature. This study provides a deeper understanding of the dynamics of solitons in fractional media, which could be useful for modelling soliton propagation in systems where traditional integer-order models fail to capture essential behavior.