Objective: Cryptotanshinone (CTS) is a compound with anti-inflammatory, anti-bacterial, anti-oxidative and anti-aggregant functions. We aimed to determine the effects of CTS on α-naphtilthiourea (ANTU)-induced acute pulmonary edema.Materials and Methods: In this study, 4 groups (control, sham, ANTU and ANTU+CTS) were established from a total of 40 rats. The ANTU+CTS group received intraperitoneal CTS for seven days, and both ANTU and ANTU+CTS received an ANTU administration for the induction of peripheral effusion. Four hours after the ANTU administration, the rats were subjected to a forced swim test and were decapitated. Swimming times of rats, amount of pleural effusion (PE), lung weight (LW)/body weight (BW), and PE/BW ratios were determined.Results: At the end of the experiment, PE was not detected in the lungs of control and sham group rats. It was determined that the PE, LW/ BW and PE/BW decreased statistically, while swimming time increased after acute pulmonary edema in the CTS group (p<0.05).Conclusion: CTS showed a protective effect against acute pulmonary edema, which indicates that it may be used as a new therapeutic agent against pulmonary toxicity.