This thesis examines mood selection in Argentine Spanish with epistemic adverbs considering the independent variables of certainty, temporal reference, and epistemic adverb. It is the first known study to investigate mood selection with the epistemic adverb capaz. A sentence completion task included 24 written contexts, each followed by a sentence with an epistemic adverbial to be completed with a verb, either in the indicative or subjunctive. The contexts contained information that made participants Certain (N = 12) or Not Certain (N = 12). Within the Certain and Not Certain contexts, four contexts expressed events in the future, four in the present, and four in the past. The level of certainty in the future, present, and past contexts was verified through a norming procedure. Finally, two epistemic adverbials, capaz and quizás, were tested in each context. All 117 participants completed a sentence in each context, half with capaz and half with quizás, without repetition of contexts. Results from a mixed model, examining the main effects, supported prior studies of mood in clauses with epistemic adverbs by indicating that temporal reference had a significant effect on mood selection. Mood was used distinctly in contexts with future, present, and past temporal reference, with the most subjunctive selected in future contexts (62%), less subjunctive selected in present contexts (42%), and the least subjunctive selected in past contexts (18%). Results also indicated that certainty did not have a significant effect suggesting that the cognition of mood selection with epistemic adverbs does not take into account certainty. There was no difference found between the sentences with capaz and quizás, indicating that the two lexical items exhibit comparable mood selection.