The present study intends to investigate English used by VTS officers in Boushehr province port controls (coast stations) according to the standards of marine communication phrases. Participants of the study were 35 VTS officers working in Boushehr province port controls. Two tests including a pretest, according to participants' previous knowledge and a post-test were given to the participants before and after a training course. The tests were consisted of four parts and 30 items that assessed comprehension, knowledge of technical marine vocabulary, phrases and structure. There was a week interval between the two tests in which a specially designed booklet was handed out to the participants. Also, four sessions of online training, two hours for each session, were held. The booklet was specially designed for VTS officers, consisting of the basic communication phrases, technical vocabularies and their explanation in plain English which are easily understandable for users. The keywords in each phrase were also bolded to show the most important parts of them. Finally, a comparison between maritime English and general English was made to portray the differences between the two registers. To analyze the data, descriptive statistics and a T test were used. Results of the study revealed that the training course had a significant change on the learning of the participants and consequently their technical vocabulary. The results of the study have useful implications for marine course designers, authors and ESP teachers.