Genjutsu are techniques that are employed in the same fashion as ninjutsu, requiring chakra and hand seals. However, the primary difference between the two is that the effect of genjutsu is illusory, creating chakra imbalances in the victim's brain, causing a disruption in their senses. This is often used to create false images or cause pain from trauma (because the body is led to believe it is in pain, and it feels real), however there are plenty of other uses depending on the situation. They are not used as often as ninjutsu because they don't physically harm the opponent, but several crafty characters have made themselves well known for their great execution of genjutsu. Genjutsu is created when a ninja extends their chakra flow through the cerebral nervous system of their opponent to control their mind's chakra, thereby affecting their five senses. Genjutsu is translated as "Illusionary Techniques"To combat the effects of genjutsu, there are two options. The first option is for the ninja to stop the flow of chakra in their body, and then apply an even stronger power to disrupt the flow of the casters chakra. This can also be done by an unaffected ninja. The second option is for the affected ninja to hurt himself. Genjutsu attacks usually will require a lot of skill, and if performed incorrectly will not work. Because of this, genjutsu is most often used by ninja with very precise chakra control and very high intelligence. These types of attacks use up a high amount of chakra and need perfect hand seals. Because of this they're most often used by a fighter with very high amounts of chakra or as a last resort. Genjutsu fittingly falls under the broad category of Yin Release.

Because genjutsu affects activity throughout the prosencephalon structure of the brain, humans, dogs and other species of mammal are therefore all affected by genjutsu; however, the kikaichū, like all insects, lack such a structure to their brains, and so do not even notice it: as Shino Aburame put it, insects are ruled almost solely by five powerful senses alone, which makes them immune to genjutsu and gives the Aburame clan an ability to detect it when nobody else can.

Many shinobi have stated that among genjutsu the most dangerous are those that affect the opponent with sound allowing the user to stay out of sight.

Combating Genjutsu

To combat the effects of genjutsu, there are several options:

• The ninja needs to stop the flow of chakra in their body, and then apply an even stronger power to disrupt the flow of the caster's chakra; this is called Genjutsu Dissipation (幻術解, Genjutsu Kai). This can also be done by an unaffected ninja by applying a sudden surge of chakra into the affected person. In addition, tailed beasts can break their jinchūriki out of genjutsu in a similar fashion if they have a good enough cooperation.
• Another is through intense pain not caused by the genjutsu and utilising the resulting pain to bring their senses back in order (of the first two options, the latter seems more effective in most situations, or at least is the easiest).
• Another option is accessible only to Sharingan wielders. Members of the Uchiha clan can break or see through genjutsu using their Sharingan. Breaking Tsukuyomi is possible with an ordinary Sharingan, but requires a lot of skill.
• Sharingan wielders can also use their dōjutsu to liberate each other from genjutsu. Through eye contact, they are able to literally insert themselves into each other's genjutsu freely allowing them to break whatever genjutsu it is that imprisons their comrade.
• Ordinary people can sometimes train their eyes (without Sharingan) to break genjutsu through unknown means.
• One can prevent a person from casting genjutsu using obstructive techniques like the Hiding in Mist Technique to prevent one from being trapped by an ocular genjutsu as Zabuza demonstrated against Kakashi.
• In the anime it was shown that strong smells like that from the Chilli Pepper Bombs, can counteract genjutsu.

In spite of these methods, some forms of genjutsu like Tsukuyomi and the Demonic Illusion: Toad Confrontation Chant may not be broken easily, either due to their near-instant effect like the former, or their ability to render one unconscious and paralysed altogether like the latter. In addition, one must realise that he or she is under the effects of genjutsu before attempting to break out of it. This can be done by observing the changes in one's own chakra with a chakra-sensing ability.