Natural ventilation is an effective strategy for greenhouse microclimate control and energy conservation. However, its performance is commonly evaluated based on air exchange rate, while its impact on thermal conditions within the crop growth zone remains less explored. This study comparatively evaluated wind-driven natural ventilation and wall-mounted solar chimney-assisted natural ventilation in a greenhouse located in the hot-arid climate of Ahvaz, Iran, using three-dimensional computational fluid dynamics simulations. Analyses were conducted under realistic temperature, solar radiation, and wind conditions during March, April, and October. The wind-driven system achieved a higher ventilation capacity, with an average air exchange rate of 5.36 h⁻¹ compared with 1.75 h⁻¹ for the solar chimney-assisted system. Despite this, the solar chimney produced a more stable and organized airflow pattern, reducing stagnant zones and air recirculation within the greenhouse. As a result, the average canopy temperature decreased from 38.93 to 36.96 °C, the temperature uniformity index increased from 0.75 to 0.91, and the canopy cooling effectiveness index improved from 0.14 to 0.54. The solar chimney also achieved an average thermal efficiency of 6.63%. The findings demonstrate that air exchange rate alone is insufficient for evaluating natural ventilation performance. Greater emphasis should be placed on microclimate quality and thermal conditions within the crop growth zone. Overall, the wall-mounted solar chimney improved airflow organization and thermal performance, highlighting its potential as a passive and sustainable solution for greenhouse climate control in hot-arid regions.