We report an elderly patient who developed severe delirium and extrapyramidal signs after initiation of lithium-olanzapine combination. On hospital admission, serum levels of lithium were found to be 3.0 mM/L which were far above toxic level. Immediate discontinuation of both drugs resulted in complete resolution of most of the symptoms except for perioral dyskinesia which persisted for three more months. We critically discussed the differential diagnosis of lithium intoxication and assessed confounding factors which induce delirium and extrapyramidal signs related with combination therapy of lithium and olanzapine.