Alloying the catalyst with an ancillary element is a promising strategy to mitigate CO poisoning. One of the advantages of this strategy is that it allows a reduction in the Pt loading, making them more attractive for commercialization. It is desirable that the bimetallic catalyst should maintain at least the same catalytic activity as Pt, as well as improve the selectivity towards different poisons. Several Pt-based bimetallic systems have been found in the last years for CO oxidation. For instance, Pt-Ni/γ-Al 2 O 3 , Pt-Fe/GA, Pt-Fe/γ-Al 2 O 3 , Pt-Sn/AC, Pt-Ru/SiO 2 and Pt-Re/SiO 2 outperform their monometallic counterparts with higher CO conversion rates. The enhancement of the bimetallic catalysts is usually ascribed to ligand (electronic) and/or bifunctional effects. Ligand effects occur when the alloying element modifies the Pt electronic structure (e.g., electron donation and back-donation capacity of Pt) without directly participating in the reaction, while in bifunctional effects the promoter becomes an active component either by forming new bimetallic active ensemble sites or offering new single active sites with different adsorption properties (dual adsorption). This dual adsorption can be achieved by incorporating oxophilic promoters into Pt so that the oxygenated species now adsorb preferentially on them, leaving the Pt sites free for CO adsorption and thus, facilitating CO oxidation. Germanium has been demonstrated to be a promising promoter for Pt. In the past, it has been used to boost the performance of Pt catalysts in a variety of reactions such as the CO electro-oxidation, naphtha reforming and alkane dehydrogenation. Previously, we showed that alloying small-size Pt clusters with Ge significantly diminishes the CO poisoning, as the interaction between Pt and CO is weakened upon alloying. Furthermore, the composition in such bimetallic catalysts might have a great influence in their physico-chemical properties. Building from these results, in this work, we combine first-principles calculations with microkinetic modeling to determine the role of Ge in the CO oxidation by Pt-Ge bimetallic clusters supported on MgO(100). Our aim is to verify whether the reduction of CO poisoning found thereof translates into an improvement of the catalytic activity and what PtGe composition provides the best performance for this reaction. The influence of the Ge concentration on the CO and O 2 adsorption properties and the catalytic behavior is thoroughly studied. A concise mechanistic study of CO oxidation is carried out by exploring and unraveling the kinetic details of the two main pathways, viz., Langmuir-Hinshelwood (LH) and Eley-Rideal (ER), along with the electronic reasons behind the observed behavior. In this way, we demonstrate that it is possible to change the bistable kinetics towards a reactive and CO poisoning-free region by adjusting the promoter content on PtGe catalysts.