Overwatering is the most common cause for yellowing of sago palm leaves. When the plant receives too much water, the root system is unable to draw the necessary oxygen and nutrients from the ground, resulting in discoloration.
Although the entire plant can display yellowing, the leaves that receive the most exposure to the sun are often the first to be affected. Sun scorch, another name for this yellowing effect, can also occur in plants that do not get the proper fertilization or are planted in soil without the proper pH. To help prevent this, sago palm plants should be fertilized with a fertilizer that is high in nitrogen.