Aripiprazole is the atypical antipsychotic which has lesser extrapyramidal side effects. Aripiprazole once monthly was recently developed as a long-acting injection (LAI) for intramuscular administration. We presented a case that developed akathisia after the first LAI of aripiprazole. The akathisia symptoms occurred after the first dose of LAI and there was not any sign of akathisia during his oral treatment with aripiprazole. The clinicians should manage the administration of LAI carefully and observe the possible side effects.