Quest for high ion-conducting solid electrolyte materials for sodium-ion batteries has been tremendously increasing. Glass materials are a potential solid electrolyte for high-energy Na-ion batteries. Nevertheless, the effective research on glass materials for their applications in Na-ion batteries is dawdling due to its low ionic DC-conductivity and poor understanding of the dynamics of mobile cations. Herein, we have attempted to address the effect of substitution of NaF for Al₂O₃ on the conductivity of Na₃Al₂P₃O₁₂(NAP) glass (mol%: 37.5P₂O₅–25.0Al₂O₃–37.5 Na₂O). Raman spectra reveal that the increase in the substituent NaF concentration significantly affects the coordination of Al³⁺ and the distribution of sodium cations in the network structure of NAP glass. Impedance spectra reveal that the change in conductivity of NAP glass with an increase in the NaF concentration is highly dependent on a specific temperature range. At a lower temperature range, (<150 °C), the conductivity increases initially with the increase in NaF concentration and it decreases with any further increase in the NaF concentration; whereas, at temperatures above 150 °C, the conductivity increases continuously with an increase in the NaF concentration. The frequency-dependent AC-conductivity has been analyzed using the time-temperature scaling principle (TTSP) based on Summerfield and Ghosh scaling procedures to probe the ion conduction mechanism. The NAP glass that contains low NaF concentrations (<7.5 mol%) obeys the AC-conductivity scaling, i.e., it satisfies the TTSP principle, with respect to temperature based on the Summerfield scaling procedure; this indicates that the sodium-ion dynamics are independent of the temperature. The scaled AC-conductivity curves for NAP glass containing high NaF concentrations (>10 mol%) have deviated from Summerfield scaling and further indicate that the fraction of sodium-ions responsible for the ionic conductivity is decreasing with an increase in the temperature. Scaling of AC-conductivity curves for all the glass samples using the Ghosh procedure suggests that the number density along with the hopping distance of sodium ions changes with increasing temperature. The Modified random network structural model has been further utilized to explain the variation in the NAP glass conductivity with an increase in the NaF concentrations. The outcome of this work will certainly aid in designing the chemical compositions of glasses for the development of solid electrolyte materials for their applications in Na-ion batteries.