Multistage mass spectrometry (MSⁿ) experiments reveal that gas phase silver iodide cluster cations, Ag_nI_m⁺, are readily built up in a stepwise fashion via ion–molecule reactions between mass selected silver (Ag₃⁺ and Ag₅⁺) or silver hydride (Ag₂H⁺ and Ag₄H⁺) cluster cations and allyl iodide, in contrast to their reactions with methyl iodide, which solely result in ligation of the clusters. The stoichiometries of these clusters range from 1 ≤ n ≤ 5 and 1 ≤ m ≤ 4, indicating the formation of several new subvalent silver iodide clusters. Collision induced dissociation (CID) experiments were carried out on each of these clusters to shed some light on their possible structures. The products arising from CID of the Ag_nI_m⁺ clusters are highly dependent on the stoichiometry of the cluster. Thus the odd-electron clusters Ag₄I₂⁺ and Ag₅I⁺ fragment via loss of a silver atom. In contrast, the even-electron cluster ions all fragment via loss of AgI. In addition, Ag₂I₂ loss is observed for the Ag₄I₃⁺ and Ag₅I₂⁺ clusters, while loss of Ag₃I₃ occurs for the stoichiometric Ag₅I₄⁺ cluster. DFT calculations were carried out on these Ag_nI_m⁺ clusters as well as the neutrals associated with the ion–molecule and CID reactions. A range of different isomeric structures were calculated and their structures are described. A noteworthy aspect is that ligation of these silver clusters by I can have a profound effect on the geometry of the silver cluster. For example, D_3h Ag₃⁺ becomes C_2v Ag₃I⁺, which in turn becomes C_2h Ag₃I₂⁺. Finally, the DFT predicted thermochemistry supports the different types of reaction channels observed in the ion–molecule reactions and CID experiments.