The main advantage of using the Communicative Language Teaching approach is that it encourages all students to participate in the lesson, which otherwise would not be the case, as many people feel that they do not use the skills outside the classroom. CLT sometimes focuses on useful aspects of the language that people might be able to use if they visited the country in question. This approach is also great for mixed ability classes, which are normally more difficult to teach, because the active communication between people allows everyone to contribute to the level they are able to reach.
In order to judge whether language teaching has been a success, the teacher must be able to understand the student. However, the results from this can be misleading if the teacher and students are all from the same place, because if the errors result from the influence of the original language, the teacher will still understand, even if a native speaker of the foreign language would not. Therefore, sometimes an adapted method is used where the teacher pretends they understand only the same as a native speaker.
The main disadvantage of the Communicative Language Teaching approach is that it can place too much emphasis on the spoken aspect of the language at the expense of the written skills. Spelling, punctuation and grammar, which are all important, will not be taught as much as they would be if another teaching method were to be used.