The Airflow rate through a two-story building with a courtyard, with and without trees, was estimated and compared with that of a building without a courtyard. The building and the courtyard were of square shapes, each 10 m to the side. The courtyard walls were 3m high and two separate trees of spherical, cylindrical and conical shapes were considered in the yard. The courtyard was directly south of the building and a wind angle of zero degree was considered when the wind was blowing directly from the south. It was found that when the wind angles were between 0 to ± 90 degrees, the Airflow rate through the building was reduced when compared with the building without a courtyard. The presence of trees in the courtyard further reduced the Airflow rate. When the wind angle was 180 degrees, i.e., when the courtyard was in the lee-ward side of the wind, the Airflow rate through the building was increased, and the presence of the trees in the courtyard further increased the flow rate. By considering the wind speeds and directions for the cities of Ahwaz, Kerman, Mashad, Shiraz, Tabriz and Tehran, Iran, the Airflow rates were estimated for the buildings located in these cities. The effect of a courtyard and its trees in reducing the Airflow rates (or increasing it, under special wind directions) were then determined.