"The Old Bulgarian Noun Phrase: Towards an Annotation Specification" addresses the issue of application of modern linguistic approaches to historical language data in a corpora-oriented approach. The study combines a linguistic analysis of Old Bulgarian diachronic data with a proposal for an annotation specification for the nominal categories. Ca. 10,000 word forms from an Old Bulgarian manuscript - Codex Marianus, were annotated. The basic structure of the Old Bulgarian noun phrase is outlined along the DP hypothesis. A linguistically motivated word-level annotation specification is proposed with separate annotation levels for the morphological description and for the functional status of the elements. The basic linear patterns of the Old Bulgarian nominal expression, duscussed in this study, can be applied further to other texts through phrase structure rules for the purposes of semi-automatic annotation of historical corpora.