This chapter outlines the development of morphosyntactic alignment in Armenian from its pre-attested stage to modern forms of the language. For the most part, Armenian follows a nominative–accusative alignment pattern; the only exception occurs in the periphrastic perfect in Classical Armenian. This tense shows tripartite alignment: subjects are marked as nominative, agents as genitive, and objects as accusative. This alignment split prevails until the end of the Classical Armenian period. The origin of this alignment pattern lies in the contact with the West Middle Iranian language Parthian from which Armenian has borrowed heavily in several linguistic domains. The Armenian perfect and its alignment are the grammaticalised result of pattern replication, by which the Parthian ergative–absolutive past tense is borrowed into Armenian and there realised by means of the participle. The change from ergative–absolutive to tripartite alignment is based on morphosyntactic reanalysis of the object case.