The present research aimed to compare the effectiveness of promethazine and diazepam in patients suffering from acute peripheral vertigo. This is a double blind clinical trial with a sample of 154 patients visiting the emergency section of Shahid Mohammadi Hospital in Bandar Abbas in 2017-18. The participants were randomly divided into two groups of 77, one treated with intravenous promethazine (50 mg) and the other with intravenous Diazepam (10 mg). The severity of vertigo was measured qualitatively and quantitatively 20 minutes later in both groups. Participants were 46 (29.9%) male and 108 (70.1%) female visiting the emergency section of hospital. The mean score of vertigo severity in Promethazine group was 44.44±17.94 and that of Diazepam group was 2.49±+3.87. The severity scores before and after the treatment in promethazine group were respectively 7.75±1.59 and 2.72±1.93. The mean scores of vertigo severity before and after the treatment in promethazine group was -5.04+2.10 and in the diazepam group it was -3.83+3.09. The intergroup difference was statistically significant (p=.013). The results revealed that intravenous promethazine and diazepam applied 20 minutes after prescription are both effective in controlling the severity of vertigo. Considering the probability of occurrence of extrapyramidal side-effects it can be suggested that the infusion of this medication be done slowly and take longer time. Meanwhile, vital signs should be precisely controlled.