In this paper, we focus on a recommendation approach for collaborative decision-making. This recommendation is possible by designing an ontology in a first step. The construction of this ontology is based on a state of the art on collaborative decision-making, on ontology engineering and on collaboration engineering. An eight-step ontology development methodology was adopted and implemented to design the ontology. A corpus made up of one hundred and seventy-seven (177) documents was the starting point for the extraction of terms from the ontology and the Unified Modeling Language (UML) language is used as a description language of the ontology. This ontology is the starting point for a facilitation support system in a collaborative decision-making process. In a second step, we defined rules, based on our expertise on collaborative decision-making, used to guide a group of decision maker or a facilitator.