This paper investigates the behavior of reduced web section (RWS) steel-concrete composite (SCC) beam-to-column connections with circular web openings through a comprehensive finite element (FE) analysis following experimental and computational studies. Results showed that the presence of a circular web opening is effective to move the plastic hinge away from the column shear panel zone and the main connection components including the welding beam-column welding area, and hence, significantly improve the ductility and energy dissipation of the connection without critically affecting its capacity. The composite action was not considered in the literature to account for the severest case (slab acts as load only) in terms of load carrying capacity. However, this study proves that the composite effect has a decisive role in the calculation of the ductility and rotational capacity, and if not considered may result in an overestimated ductile behavior. On the other hand, in cases where composite action is not provided, depending on the particular flooring system, noncomposite steel connections may be considered where the ductility and energy dissipation gains are definitely higher but the load carrying capacity is lower. This paper establishes the comparison between composite and noncomposite connections and concludes that the contribution of the composite action to the load carrying capacity is higher with the increase of the beam web opening diameter. Therefore, the calculated negative load carrying capacity tends to be very conservative if the composite effect is neglected when a large opening diameter is used.