Al‐7 w/o Ni alloys were unidirectionally solidified at different solidification rates (R) and thermal gradients (GL). Al3Ni whisker morphology is discussed in terms of solidification parameters and also correlated with alloy strength. For a given thermal gradient (GL=17°C/cm), low solidification rates give rise to large whisker spacing (λ) and size (d), maintaining the constant value ofλ/dbetween 2.0 and 2.3. Interrupted growth of Al3Ni whiskers along the solidification direction causes a reduction inλ/das compared with that for continuous whiskers (λ/d=2.8). Tensile strength for continuous fiber strengthened composites is calculated to be 33.6 kg/mm2, whereas the experimental value ranges from 18 to 19 kg/mm2. A considereable decrease in strength is attributed to theGL/Rbeing much smaller (10°C.hr/cm2) than the theoretical value (300°C.hr/cm2). Longer Al3Ni whiskers due to lower solidification rates can be explained by the interface precipitation model proposed by Honeycombe and Davenport.