Background: Aflatoxicosis in ducks is reckoned as a challenge for nutritionists worldwide, for its adverse impacts on growth. A study was conducted to ascertain the precise level of Aflatoxin-tolerance in White Pekin ducklings during juvenile ages. Methods: Day-old-ducklings (240) were randomly distributed into 3 experimental-groups viz., Control ( less than 0.5 ppb), T1 (200 ppb), T2 (400 ppb) and reared for measuring weekly growth, feed efficiency and blood biochemical changes, with treatments terminated at 6weeks age. Result: There was significant depression in live weights for both dietary-toxin groups from 2nd week onwards till completion. Mortality (0-6 weeks) was 85% in T2, while T1 was in between control and T2, both for mortality (45%) and morbidity. Feed-consumption and conversion for either toxin groups remained significantly (p≤0.05) poor, with T2 resulting in erratic FCRs, ranging from 1.23 to 4.95, across weeks. A typical AFB1-induced lameness in ducklings beyond 3 weeks of AFB1-exposure, emerged as a hallmarked morbidity, in varied proportions, in T1 and T2, but not in control. The study confirms that acute-depression of juvenile growth and high-morbidity are distinct outcomes from AFB1’s presence in Pekin diets @ 200 ppb level or higher, with such leg deformities emerging as hallmarked features of Pekins reared on AFB1-spiked diets. It can be concluded that, while the AFB1 content of juvenile White Pekin ducks should be kept limited to the recommended safe levels ( less than 10 ppb); exceeding a threshold of 200 ppb is sure to cause poor growth and FCR, with adverse blood biochemical changes, high mortality, morbidity and lameness.