Citizens’ engagement is considered as one of the important dimensions for the development of smart cities since, in the vision of a city of the future (smart city), citizens will be more and more involved in the decision-making process of different issues related to the development of a city. In this context, policy makers face a decision problem where they have to integrate a new dimension, which is the voice of the citizens’ decision. This article proposes a tool based on multicriteria decision making methods to provide decision makers with the best alternative(s) that are based on citizens’ opinions. In order to tackle the potential interdependencies between criteria and also between alternatives in the selection process, we apply a hybrid model integrating the analytical network process and an extended version of technique for order performance by similarity to ideal solution to support group decision-making. The proposed model is applied in the context of participatory budgeting (PB) where citizens decide on the projects in which the money can be invested. This process is complex since it encompasses multiple interdependent criteria that may be conflicting with each other and that are used to take decisions. To illustrate our approach, we will apply the proposed technique for the case study of La Marsa, a city in the north of the capital Tunis (Tunisia) that adopted, since 2014, a PB strategy in which citizens proposed alternatives on how an amount of money can be used to lighten specific streets in the city.