Loss of agricultural produce in acidic soil due to aluminum (Al) toxicity is a major problem worldwide. In the earth crust, Al is one of the plenteous minerals and is useable to plants when only the pH of the soil is acidic (pH < 5). In acidic soil, Al exists in Al3+ (also called exchangeable Al) which is water soluble and is easily taken up by plants. The primary site of damage infliction in plants is roots, which is visible within few hours of exposure to Al toxicity in acidic condition. Al3+ interacts with other ionic species or mediates in the activities of other species to cause ionic imbalance causing toxic symptoms. Also, other minerals and ionic species interact with Al3+ to reduce its toxic activity when exogenously applied to crop plants. In this chapter, we discuss all these aspects of Al toxicity in details.