The incorporation of iron into peralkaline silicate glasses significantly impacts their structural and thermal properties. Here we investigate how addition of iron influences the network connectivity (short- and medium-range order) and glass transition temperature (Tg) with particular regard to the iron speciation and the Fe2+ and Fe3+ coordination state. We also found a sort of tipping point in iron concentration beyond which the short-range structures evolve linearly with density while the medium-range structure deviates. This behavior seems related to a re-enrichment of tetrahedral units triggered by iron self-compensation effect explaining the observed jump in Tg.