Economic, political, and technological uncertainties require organizations to prepare adequately for new events that occur each day. Economic crisis, changes in the policies of each country and technological developments are classic examples of these changes in organizations. Seasonality is one of the economic phenomena that occur, and different forms of management are required. The seasonality that is described as a systematic and temporal imbalance of the tourist phenomenon that does not need to be regular, caused by the climate or by the vacation periods, and is based on the consumer behavior that can be expressed in terms of the number of visitors, traffic, highways, jobs, and tickets at attractions. Therefore, through a careful analysis of seasonality, it is possible that the losses are predicted, and the negative impact is not so grotesque on the company. For this, it is good that the manager uses the cost assessment methods to assume the seasonality of sales and thus be able to guard against the negative effects of the same. The objective of this research is to understand how owners of micro and small businesses in coastal cities consider themselves entrepreneurs or not and how they deal with obstacles such as seasonality through cost management. The methodology used was based on an exploratory and bibliographic research with a qualitative approach, seeking to analyze the triad: Entrepreneurship, Seasonality and Cost Management. The field research was applied through a semi-structured questionnaire to the sample of 100 Microentrepreneurs in the trade of goods and services in Caraguatatuba and São Sebastião, central cities of the North Coast of São Paulo. The main results show that most of the interviewed entrepreneurs perceive a certain impact caused by seasonality, understand the use of Cost Management to improve their processes and are adapted to one of the main costing methods highlighted by the bibliography.