The diversity of phytochemicals could serve as a source of useful drugs against many plant diseases. The present study deals with phytochemical analysis of larkspur (Delphinium ajacis) and their antimicrobial activity against Colletotrichum gloeosporioides, Alternaria solani, Pyricularia oryzae and Rhizoctonia solani. In this paper, the dried stems, leaves and flowers of Delphinium ajacis were extracted using standard assays to evaluate the phytochemical constitution. Qualitative analysis of phytochemical constituents was performed by the well-known tests protocol available. The phytochemical screening revealed the extract richness in alkaloids, tannins, terpenoids, phenols and saponins. The study also includes preparation of different extracts by successive solvent extraction for detail analysis. Fluorescence analysis of these extracts were also noted under ordinary and UV light to signify their characteristics. The in vitro antimicrobial activities were also investigated by using disc diffusion methods. The leaf extract exhibit marked antimicrobial activity against plant pathogens. It may lead to development of potentially effective and environmental friendly alternative chemicals to control plant diseases.