Aeration in the waters of rivers and streams is very important to the quality and existence of aquatic life. If the overfall jets downstream of weir structures plunges into a plunge pool, entrained air bubbles will contribute to aeration. This paper investigates sharp-crested weirs having different cross-sectional geometry and their effect on the air entrainment rate. It is demonstrated that the air entrainment rate of a 30° triangular sharp-crested weir is better than that of the other sharp-crested weirs tested. Moreover, variation in the number of V-notches over the width of the weir plate was studied for 30° triangular sharp-crested weirs. The 30° triangular sharp-crested weir with two V-notches was found to have higher values of air entrainment rate.Key words: aeration, air entrainment rate, plunging overfall jet, sharp-crested weir.