For the purpose of preparation of this doctoral dissertation, a survey was conducted on the feasibility of collecting data and information on the properties of sewerage systems in the Republic of Croatia and on the costs of sewerage systems maintenance. The data were collected through questionnaires sent to companies managing sewerage systems. As a result of collected data and information on the properties and costs of sewerage systems’ maintenance, a database was created. The database was used to develop a maintenance cost estimation model for sewerage systems. The analysis of such a database and literature review has enabled the identification of variables that are significant in estimating maintenance costs and developing the maintenance cost estimation model of the sewerage system. Also, data structure and maintenance costs structure of sewerage system have been developed enabling easier monitoring of annual costs. This approach ensures mutual comparability of maintenance costs on sewerage systems in the Republic of Croatia. The possibility of applying linear regression in developing the maintenance cost estimation model of sewerage system has been established. A maintenance cost estimation model of sewerage system has been defined. In addition to this, the variables that most affect the maintenance cost of sewerage system have been identified. Advantages and limitations of the maintenance cost estimation model have been defined. The greatest advantage of the maintenance cost estimation model is the simplicity of use with a small amount of the required sewerage system data, which are already available at the beginning of the design elaboration process. By applying the maintenance cost estimation model, it is possible to plan a budget for the maintenance of sewerage systems at the level of a particular company in the Republic of Croatia and for specific time period. The use of this model is expected to improve the efficiency of sewerage system maintenance and use of the life cycle cost method, since it will be possible to estimate the maintenance costs of sewerage systems already during the design process.