In the present paper, we aim to analyze the noun phrase in Dosoftei’s writings, focusing on the syntactic function of determiner. The paper will be divided into two parts, the first one dealing with the theoretical framework and the second one being dedicated to the analysis of the investigative corpus. After providing a definition of the noun phrase and a description of the kind of adjuncts it might select, we will provide an overview of determination and determiners. Then, we will observe the peculiarities of the determiner as a syntactic function introduced in the Basic Grammar of the Romanian Language. As far as the investigative corpus is concerned, we will first discuss the class of substitution of the determiner. We will then proceed to the description of complex noun phrases, in which determiners co-occur with other syntactic positions. We will first discuss the internal structure of each noun phrase and then we will provide examples to support our demonstration. We will take into account definite as well as indefinite determination. All in all, the examination of the investigative corpus will reflect the complex possibilities of structuring the noun phrase, illustrating the diversity of syntactic constructions in Old Romanian, as far as the determiner is concerned.