This paper focuses on the pragmatic application of vague language in commercial advertising which is viewed as a persuading strategy by the advertisers. It is intended to be a qualitative study based on the data collected from newspapers, magazines, etc. that is, from printed commercial advertisements. The theoretical framework is constructed on the basis of Jef Verschueren’s (2000) linguistic Adaptation Theory.As a strategy of persuading or influencing, this pragmatic application relies on diversified linguistic structures to achieve its functions. Therefore, the advertisement writer needs to manipulate her language so as to select an appropriate linguistic structure which can perform her strategy. Through careful scrutiny of the data, we summarize several linguistic means of vague language in advertising, namely, the word itself is vague, some figures of speech bring about vagueness, and/or the meaning of the sentence is vague. Thus, the variability of this application is demonstrated through its ways of linguistic manipulation.As to why vague language is employed in some specific advertisements, we have discussed the adaptive process to deal with this problem. It has been found out that pragmatic application of vague language is employed to adapt to diversified cognitive or emotive needs of the audience. A scrutiny of the contextual correlates adapted by the pragmatic application enables us to draw the conclusion that the choice of vague language in advertising is, as a matter of fact, the result of linguistic adaptation.After the analysis of how and why vague language is employed in advertising, we have discussed the specific functions of the application of vague language in advertising. The present investigation has led to the finding that this application can give the right amount of information, improve the appropriateness of the advertisement, deliberately withhold information, lessen face-threatening effects andcreate a humorous effect.Pragmatic application of vague language is a pervasive language phenomenon in advertising. A fairly dynamic and systematic research may prove both its theoretical and practical values in the linguistic field.