Many studies investigating the ecology and evolution of mosquitoes rely on morphometric measurements related to body size to estimate fecundity. Determining the most reliable estimators of fecundity is therefore an important methodological consideration. We compared the relative accuracy of pupal mass and wing length in predicting the fecundity (number of mature stage IV follicles of the first gonotrophic cycle) for (1) Aedes albopictus (Skuse) reared in the laboratory, (2) Aedes geniculatus (Oliver) reared in the laboratory, and (3) A. geniculatus that completed their larval development in water-filled tree holes (their natural habitat) in the field. In all cases, pupal weight and wing length provided highly significant and equally accurate indicators of fecundity. Furthermore, the measurement error (1 − repeatability) for both traits was ≤1%. Our results indicate that either pupal mass or wing length can be used with confidence to predict fecundity in these two aedine mosquitoes.