Gradual decline in cognitive function and behavioral changes are characteristic in degenerative dementia. Although acute to subacute subcortical lesion can affect behavior and cognition, few reports have described both cognitive and behavioral deficits in patients with right basal ganglia lesion. An 82-year-old man presented with memory impairment, pathological crying, delusion and other psychological symptoms that developed insidiously over the previous 2 months. Initially, the patient had been diagnosed with degenerative dementia, but brain MRI showed the hematoma in the right basal ganglia. Our case shows that cognitive dysfunction, behavioral and psychological symptoms including pathological laughing and delusion can be developed concurrently by the lesion of the right basal ganglia. Our case suggests that cerebrovascular disease should be considered in elderly patients presenting with subacute cognitive and behavioral deterioration, even when there were no other neurological signs.