In the real world, values are not always accurate, since vague and uncertain data exist in many applications. In this paper, a single-server finite capacity Markovian queuing system being called M/M/1/N with encouraged arrivals is considered. The different arrival rates, service rates and processing times of labor/duties are usually supposed to be uncertain. Therefore, we describe the theory of queuing in a vague environment in which encourage arrivals rates and service rates are considered to be vague numbers. Then, economic analysis of the model is presented by developing a cost model proceeding to exert uncertainty of the primary information when some of the parameters of the models are vague.