In structural engineering, either structure safety or sustainable design of structure is an important parameter, which must be considered. On the other hand, the issue based on the creation of an optimum model toward any design in the structural engineering area becomes possible by fulfilling the mentioned design conditions. In this regard, in the present study, a reinforced concrete (RC) beam model with a T-shape cross-section was tried to optimize in the way of providing the minimum carbon dioxide (CO2) emission from the structural materials comprised of both concrete and steel. In this direction, optimization applications were provided according to different concrete grades in terms of compressive strength, besides that optimal cost levels were also obtained for all of the design combinations. While the optimization analyses were conducted to minimize CO2 emission, a well-known metaheuristic algorithm called as flower pollination algorithm (FPA) was benefited. Therefore, both optimization outcomes and statistical evaluations of them were presented concerning the eco-friendliest, sustainable, and also conveniently cost designs through decreasing one of the detrimental factors as CO2 emission.