This multi-level (individual and collective) study examines collective decision making as it relates to the performance metric of collective decision quality. A collectivistic leadership approach is used, as leaderless collectives engaged in decision making are inherently involved in collective leadership. A multi-level conceptual model for collective decision making is introduced, which incorporates leadership and collective intelligence. Using agent-based simulations and content-coded field study data, results from both methods suggest that there is a positive relationship between individual and collective intelligence, as well as a positive relationship between collective intelligence and collective decision quality. The implications of these and related findings for future collective level research bridging the fields of decision making, leadership, and collective intelligence are discussed.