Clausal subordination is an enigmatic phenomenon in language, whose purpose cannot be explained by syntax alone. A more convincing explanation, at least for motivating subordination, relies on functional-cognitive principles, whereby subordinate events exhibit conceptual dependence. It is this dependence that motivates the use of “verb deranking” in conceptually dependent events, i.e. the loss of tense, aspect, and mood (TAM) morphology and person markings. Since the 1980s, a functional-cognitive approach has been adopted to study subordination in a range of languages, but data for Iranian languages is lacking. The aim of this thesis is therefore to provide a functional-cognitive account of subordination strategies in Old Persian. Examples of subordinate relations were found in Achaemenid-era Old Persian inscriptions, and patterns of verb deranking (and the opposite, balancing) were compared with findings from research on other languages. The results show that patterns for verb deranking and balancing in Old Persian align with cross-linguistic trends. In relative relations, verb deranking is more common in events with a relativised subject than in those with a relativised object, genitive or oblique. In adverbial relations, verb forms in reason events are always balanced, unlike in temporal, conditional, and purpose events. In complement relations, verb forms in modal, phase, desiderative, and manipulative events are consistently deranked, and they are consistently balanced in knowledge and utterance events.