The most obvious result of sibling jealousy is the conflict it creates. A jealous sibling is constantly on the lookout for ways that he can "one up" his sibling. Verbal arguments and physical fights can result from jealousy, and parents may find themselves at wit's end trying to navigate the waters of their children's conflicts. Arguments may center around anything, from taking turns to personal space, and from chores to physical possessions.

When one child is jealous of another, a common reaction is for the jealous child to give up in that area of achievement. For example, if a child is extremely strong academically, a jealous sibling might back away from even attempting to excel in schoolwork, focusing on areas, instead, in which she is able to excel. This is especially common when dealing with two same-gender children spaced closely together, such as a very talented older child and a younger child or the youngest child who is much younger than any other sibling. In each of these cases, the younger child may feel unable to compete with the older one, due to a belief that she will never be able to "catch up," anyway.

Sometimes, children are jealous of their siblings because of the unequal attention or encouragement their parents gave to them. For example, if a parent is naturally closer to one child or seems to favor that child unfairly, the other sibling may act up simply to gain the parent's attention. This may manifest itself through misbehaviors at home or in school, low grades in class, or via other concerning behaviors. Parents who witness these types of attention-getting techniques should first focus on whether they have been treating one child unfairly, and second, they should consider how they can increase positive attention so that the jealous child will feel taken care of and noticed, and he will become less jealous, as a result.

Sibling jealousy can also do a number on a child's self-esteem. When a child constantly compares himself to his more successful sibling such as in academics, sports, social prowess, or any other area, he will find himself constantly coming up short. No matter how hard he tries, he feels that he will never be able to be "great" because his sibling has already taken that title. This self-esteem issue can continue into adulthood, and can affect the way that both siblings view themselves.