Previous research has noted that verbal suppletion for ergative number agreement (i.e. agreement with the subjects of intransitives and the objects of transitives) is widespread throughout the Uto-Aztecan language family and is therefore reconstructable to Proto-Uto-Aztecan ( PUA) (Langacker, 1977). However, no previous works have systematically surveyed the attested forms of suppletion in these languages nor posited specific proposals for reconstructions of particular suppletive morphs back to PUA. We redress this lacuna by surveying the suppletive verbs in the various subgroups of Uto-Aztecan and assessing which of those are sufficiently widespread to reconstruct to PUA. We argue for specific PUA reconstructions for two verbal domains: die and kill, arguing that there were three distinct suppletive verb stems for marking these functions: *muku die.sg, *ko(i) die.pl, and *mɨɁa kill.sg. The plural form of kill in PUA was derived by adding a causative suffix *-ya to the plural stem for die, yielding *ko-ya. Other suppletive verbs in the family are not as easily reconstructable to PUA due to variation in attested forms, although some semantic functions seem to be widespread enough to be reconstructable. The PUA forms serving those functions would have been altered in different ways at different times by a lexical replacement process endemic to cases of strong suppletion, i.e. incursion (Juge, 2000). We also consider the issue of potential areal contact involving suppletion patterns in the areas where Uto-Aztecan languages are spoken, finding limited but suggestive evidence for possible areal effects involving suppletion for verbal number agreement.