This article discusses the function of a particular feature of sign language--mouth action--as it is expressed in various discourse contexts. Specifically, we examine forms of mouthing and mouth gesture as they are used in signed narrative and expository texts, highlighting the signers' choices during the production of these two text types. We propose a new perspective on mouth action types, relying on insights from the domain of discourse analysis combined with functional categories proposed in previous studies on mouth actions in sign languages. Six deaf native signers of Israeli Sign Language (ISL) produced twelve texts, yielding a corpus of 2,125 mouth actions (1,112 in narrative texts and 1,013 in expository texts). Our study points to both quantitative and qualitative differences in the use of mouth actions in the two text types. The findings emphasize the importance of the two types of mouth actions as essential means of decoding the message, and they highlight the way mouth actions serve the text and are affected by it.