The research is designed to examine communication practice in the process of diffusion of innovation in Amhara Region Agricultural Research Institute. Hence, the study was examining communication practice in the process of diffusion of agricultural innovation in Amhara Region Agricultural Research Institute that how agricultural extension workers, researchers, and public relation experts created awareness and diffused the new agricultural technologies to benefit the farmers so as to use agricultural products or technologies. Thus, this qualitative case study design which is used in-depth interview, focus group discussion and document analysis. The study was framed based on diffusion model and participatory communication theory, as theoretical framework. The finding of this study clearly shows that there is a limitation communication practice in the diffusion of innovation in the diffusion of agricultural products and services. To guide the diffusion communication work, there is no defined and clear diffusion communication strategy, the approaches are traditional means and personal, and hence the communication intervention is made only for the sake of information dissemination. Additionally the Studies show that mass media is not well communicated or used in the institution for the diffusing of agricultural technologies for the creating of awareness knowledge to the farmers. This gap could make the sustainability of diffusion agricultural technologies under question. The root cause for sustainability problem may be different but regarding to diffusion communication practice, absence of communication strategy, shortage of agricultural extension experts, and access to mass media are the main problems in the institution. To improve such gap a defined diffusion communication strategy should be designed and implemented seriously. Also it recommended that clarifying the role of communication strategies and creating awareness about agricultural technologies is a key factor to strengthen and effectively use them. Although, the farmers, researchers, and extension experts are shared emphasizing the necessity of working together for the successful implementation of these communication strategies.