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1) Background: By 2050, it is estimated that 130 million people will be diagnosed with dementia, and currently approved medicines only slow the progression. So preventive intervention is important to treat dementia. Mild cognitive impairment is a condition characterized by some deterioration in cognitive function and increased risk of progressing to dementia. Therefore, the treatment of mild cognitive impairment (MCI) is a possible way to prevent dementia. Angelica gigas reduces neuroinflammation, improves circulation, and inhibits cholinesterase, which can be effective in the prevention of Alzheimer's disease and vascular dementia and the progression of mild cognitive impairment. (2) Methods: Angelica gigas (AG) extract 1 mg/kg was administered to mildly cognitive impaired mice, models based on mild traumatic brain injury and chronic mild stress. Then, spatial, working, and object recognition and fear memory were measured. (3) Result: Angelica gigas improved spatial learning, working memory, and suppressed fear memory in the mild traumatic brain injury model. It also improved spatial learning and suppressed cued fear memory in the chronic mild stress model animals. (4) Conclusions: Angelica gigas can improve cognitive symptoms in mild cognitive impairment model mice.Nutrients 2020, 12, 97 2 of 12 Animal models are needed to study MCI and develop therapeutics. An appropriate MCI model may have symptoms aggravating with age, but with only subtle memory impairment [5]. Animal models that meet these criteria include middle-aged rodents and transgenic mice that overexpress A β at an early stage before the dementia onset [4]. Spontaneously hypertensive rats (SHRs) appear to be appropriate as MCI models for vascular dementia, since hypertensive astrogliosis, cytoskeleton breakdown, hippocampal atrophy, and cholinergic deficit prematurely appear prematurely in this animal [6][7][8]. In contrast, drug-induced memory impairment models (such as those using scopolamine, NMDA blockers, and benzodiazepines) are not appropriate because they do not represent the various aspects of MCI [5].Traumatic brain injury (TBI) is one of the most common brain injuries that causes a progressive decline of memory and cognition [9]. Unlike severe TBI, moderate to minimal TBI tends to be overlooked. However, even mild TBI can cause gradual amnesia, altered executive function, concentration disorders, depression, apathy, and anxiety [8,10,11]. In particular, repetitive head injuries, such as those caused by collision sports or motor vehicle accidents, are known to cause dementia [12]. Animal models of TBI show a decrease in cognitive function that correlates to the extent of injury, the number of impacts, and progressively worsens [13][14][15]. Therefore, the TBI model is a useful MCI research tool because it is simple, progressive, reproducible, and the severity of cognitive decline is relative to the number of impacts [16].Chronic mild stress (CMS) is a behavioral model of depression that is caused by sequential exposure to variable mild str...