The effect of boron doping in Fe50-XMn30Co10>Cr10Bx multi-component alloys on the resulting stacking fault energy has been experimentally and computationally assessed. Firstly, the fcc and hcp phases were identified together with stacking faults along their (110) planes using high-resolution transmission electron microscopy. At the same time, they were theoretically predicted through thermodynamic CALPHAD and ab-initio calculations. For the boron-free alloy, the stacking fault energy was 23.5 mJ/m2 suggesting that the deformation mechanisms relate to dislocation slip and deformation twinning. For the highest boron content (5.4 at.-%), a stacking fault energy of 43.5 mJ/m2 was obtained due to dislocation glide as a possible deformation mechanism. Thus, the presence of borides, the fcc phase stability and the boron in solid solution all contribute to increased stacking fault energy preventing the motion of Shockley partial dislocations and influencing the ɛ-hcp martensitic transformation. Finally, the boron content in the solid solution was modelled. The results suggested that the presence of Cr-B, Mn-B and Fe-B bonds point towards the formation of (Cr,Fe)2B borides as experimentally was confirmed. Thus, this research underlined the important aspects that enable understanding the alloys´ deformation mechanisms from structural and thermodynamic perspectives.