The impact of H₂ as additional reducing agent on the SCR of NO with C₃H₆ in excess oxygen, was comparatively explored over low noble metal loading (0.5 wt%), Pt/γ-Al₂O₃, Pd/γ-Al₂O₃, Ir/γ-Al₂O₃ catalysts. To gain insight into the role of H₂, the reactions NO + C₃H₆ + O₂ (R#1), NO + C₃H₆ + O₂ + H₂ (R#2), NO + H₂ + O₂ (R#3) were employed. In respect to propene oxidation, the Pd > Pt > Ir sequence was obtained under R#1, since they exhibit complete conversion at 220, 250, 325 °C, respectively; all metals exhibit moderate deNOx performances (X_NO, <40%). H₂ co-presence (R#2) promotes both the NO and C₃H₆ conversions, which is valid in the whole temperature interval investigated (50–400 °C), being more substantial for Pt/γ-Al₂O₃ and Ir/γ-Al₂O₃, less beneficial for Pd/γ-Al₂O₃. A two-maxima feature is obtained on X_NO pattern (at ∼100 and ∼230 °C) of Pt and Pd during R#2. The low temperature maximum −attributed to NO reduction by H₂- is substantially more pronounced on Pt than Pd, offering X_NO ∼90% and S_N2 ∼85%; the high temperature maximum—attributed to NO reduction by C₃H₆—is higher by ∼15% on both Pt and Pd, in respect to the values obtained during R#1, while S_N2 remained unaffected. Different X_NO pattern with one maximum is obtained over Ir, implying a synergistic interaction between H₂ and C₃H₆. This synergy is accompanied by a substantial widening of the NO reduction window toward lower temperatures and a considerable increase on both X_NO,max and S_N2 (from X_NO ∼30% with S_N2 ∼55% during R#1 to X_NO ∼70% with S_N2 ∼95% during R#2). The specific features of all reactions and metals employed are comparatively discussed.