Wind generally reduces the thermal effectiveness of air-cooled condensers (ACCs). Therefore, this study investigates wind screens as a means to improve the performance of a 20-fan induced draft ACC under windy conditions. Two wind-screen configurations are tested: walls extending above the fan platform (termed wind walls) and walls extending below the fan platform (termed wind skirts). The performance of this five-by-four ACC is evaluated using the open-source computational fluid dynamics code, OpenFOAM. The performance is first analyzed under windless operating conditions and then when the ACC is subjected to wind speeds of 3, 6, and 9 m/s directed along the shorter and longer axes of the ACC. Under windless conditions, wind walls increase the ACC’s thermal effectiveness by 1.0%. Wind skirts, however, reduce the effectiveness by 1.8%. Depending on the wind speed and direction, wind walls increase the mean thermal effectiveness of the ACC by 0.3–3.9% under windy conditions. Wind skirts, on the other hand, are only beneficial at higher wind speeds: At 3 m/s, the effectiveness declines by 1.4–2.1%; at 6 m/s, the change in effectiveness ranges from −0.4% to 2.2%; and at 9 m/s, the effectiveness increases by 2.4–3.8%. Wind walls are therefore considered more effective than wind skirts for the tested range of wind speeds.