The objective of this work was to study the promotional effect of Pt on Co-zeolite (viz. mordenite, ferrierite, ZSM-5 and Y-zeolite) and Co/Al 2O 3 on the selective catalytic reduction (SCR) of NO x with CH 4 under dry and wet reaction stream. After being reduced in H 2 at 350°C, the PtCo bimetallic zeolites showed higher NO to N 2 conversion and selectivity than the monometallic samples, as well as a combination of the latter samples such as mechanical mixtures or two-stage catalysts. After the same pretreatment, under wet reaction stream, the bimetallic samples were also more active. Among the other catalysts studied with 5% of water in the feed, (NO = CH 4 = 1000 ppm, O 2 = 2%), the NO conversion dropped to zero over Co 2.0Mor at 500°C and GHSV = 30,000 h −1, whereas it is 20% in Pt 0.5Co 2.0Mor. In Pt/Co/Al 2O 3 the NO x conversion dropped below 5% with only 2% of water under the same reaction conditions. The specific activity given as molecules of NO converted per total metal atom per second were 16.5 × 10 −4 s −1 for Pt 0.5Co 2.0Fer, 13 × 10 −4 s −1 for Pt 0.5Co 2.0Mor, 4.33 × 10 −4 s −1 for Pt 0.5Co 2.0ZSM-5 and 0.5 × 10 −4 s −1 for Pt/Co/Al 2O 3. The Y-zeolite-based samples were inactive in both mono and bimetallic samples. The species initially present in the solid were Pt° and Co°, together with Co 2+ and Pt 2+ at exchange positions. Co° seems not to participate as an active site in the SCR of NO x . Those species remained after the reaction but some reorganization occurred. A synergetic effect among the different species that enhances both the NO to NO 2 reaction, the activation of CH 4 and also the ability of the catalyst to adsorb NO, could be responsible for the high activity and selectivity of the bimetallic zeolites.