annabis use is a pervasive and increasing substance abuse particularly among adolescents and young adults. There is a strong association between cannabis exposure and psychiatric disorders. Delta-9-tetrahydrocannabinol (THC), the major psychoactive component of cannabis, has dose dependent effects and has a potential to induce psychotic symptoms in genetically vulnerable individuals, especially at high doses. The main clinical symptoms of cannabis intoxication include impaired motor coordination, euphoria, anxiety, sensation of slowed time, dry mouth, conjunctival injection, and tachycardia. Additionally, although cannabis intoxication delirium is described in DSM-IV-TR, it is a rarely reported as a clinical condition. In this presentation we report a case, which developed delirium shortly after cannabis use. Our case is a 21 year-old male, with diagnosis of “Borderline Personality Disorder+Anxiety Disorder” and with treatment of escitalopram 20 mg/day and olanzapine 5 mg/day. He has been under this medication for 2 months in his referral. He was transported to our emergency department due to the rapid changes in his consciousness, bizarre movements and behaviors like talking to himself, moving his arms and legs purposeless, trying to catch something in front, sleepiness and probably hyperesthesia. We were informed that he was normal and he took his medication of olanzapine 5 mg p.o. two hour prior to arrival. He had also history of substance abuse. His blood tests were performed and all parameters found to be in normal range whereas his vital signs, cranial CT were normal. He was not oriented and not cooperating. There was no response to verbal stimulation while he responded to painful stimuli. His consciousness was şuctuating between agitation and somnolence. Toxicological analysis was performed in order to clarify probable substance intoxication. The metabolite of tetrahydrocannabiol (THC) was detected in his urine whereas other drugs were negative. He was diagnosed to have “Cannabis Intoxication Delirium” and taken under clinical observation and follow-up in the emergency department. His symptoms ceased and his mental status returned to the normal level spontaneously within 48 hours. He was cooperating, oriented, had ability to testing reality but had anterograde amnesia including delirium period before discharge. Cannabis is the most consumed illicit drug in the world. This patient had a long period of cannabis use history but no cannabis induced disorder before. As we concluded that the delirium he experienced was induced by cannabis use, the possibility of the medication he used might have interacted with cannabis and caused delirium manifestation should be considered. Therefore, although there is sufficient data confirming that cannabis use was associated with onset of psychotic symptoms, clinicians should be aware of other clinical presentations of cannabis intoxication such as delirium, especially in patients under psychotropic medications.