Purpose: We conducted this study in order to determine clinical features and prognostic factors in adults with acute tetrodotoxin (TTX) poisoning caused by ingestion of puffer fish. Methods: In this retrospective study, 107 patients were diagnosed with TTX poisoning. The subjects were divided into two groups according to duration of treatment; Group I, patients were discharged within 48 hours (n=76, 71.0%), Group II patients were discharged after more than 48 hours (n=31, 29.0%). Group II was subsequently divided into two subgroups [IIa (n=12, 11.2%), IIb (n=19, 17.8%)] according to the need for mechanical ventilation support. Results: In multivariable logistic regression analysis, the predictors of the need for treatment over 48 hours were dizziness (odds ratio [OR], 4.72; 95% confidence intervals [CI], 1.59-12.83), time interval between onset of symptom and ingestion (OR, 0.56; 95% CI, 0.16-0.97), $PaCO_2$<35 mmHg (OR, 8.37; 95% CI, 2.37-23.59). In addition, predictors of the need for mechanical ventilation were a time interval between onset of symptoms and ingestion (OR, 0.54; 95% CI, 0.11-0.96) and $PaCO_2$<35 mmHg (OR, 5.65; 95% CI, 1.96-18.66). Conclusion: Overall, dizziness, time interval between onset of symptoms and ingestion, ${Delta}DBP$ and $PaCO_2$<35 mmHg predict the need for treatment over 48 hours, time interval between onset of symptoms and ingestion and $PaCO_2$<35 mmHg predict the need for mechanical ventilation support after acute TTX poisoning.