Herein, we present an intercluster reaction leading to new trimetallic nanoclusters (NCs) using bimetallic and monometallic NCs as reactants. Dithiol protected bimetallic MAg₂₈(BDT)₁₂(PPh₃)₄ (BDT = 1,3-benzenedithiol and M = Ni, Pd, or Pt) and monothiol protected Au₂₅(PET)₁₈ (PET = 2-phenylethanethiol) were used as model NCs. A mixture of trimetallic MAu_xAg_28–x(BDT)₁₂(PPh₃)₄ (x = 1–12) and bimetallic Ag_xAu_25–x(PET)₁₈ (x = 1–7) NCs were formed during the reaction as understood from time-dependent electrospray ionization mass spectrometry (ESI MS). Detailed studies of intercluster reaction between Ag₂₉(BDT)₁₂(PPh₃)₄ and Au₂₅(PET)₁₈ were also performed. Although both MAg₂₈(BDT)₁₂(PPh₃)₄ (M = Ag, Ni, Pd, or Pt) and Au₂₅(PET)₁₈ contain 13 atoms icosahedral core, only a maximum of 12 Au doped NCs were formed for the former as a major product and not the 13 Au doped one, unlike the previous reports of intercluster reaction. The transfer of Ni, Pd, or Pt atom from the center of icosahedron of MAg₂₈(BDT)₁₂(PPh₃)₄ to Au₂₅(PET)₁₈ was not observed, which suggests that the central atom is not involved in the reaction. Density functional theory (DFT) calculations were performed to know structures and properties of the formed NCs. This study demonstrates the use of intercluster reaction as an effective synthetic protocol to make multimetallic alloy NCs.