Code-switching in public domains has become common in Taiwan. However, little is known about the actual use of Taiwanese in Mandarin-dominant spoken media discourse. This inquiry examines the motivation behind speakers’ choice of Taiwanese when they meant to attain certain communicative effects in this setting. A detailed discourse analysis proposes that the chief motivation is linked to the association of Taiwanese or of some specific expressions in Taiwanese. Four types of association appeared. First, speakers switched to Taiwanese because of the association with certain social meanings generated in certain social contexts. Second, speakers associated Taiwanese with individual people or cultural objects because it was one of the noticeable linguistic attributes of the people or cultural objects. Third, speakers associated Taiwanese with certain expressions of ideas because certain phrasing or some specific words in a lexicon in Taiwanese could more precisely, descriptively, effectively, and/or vividly word the ideas than those in Mandarin. Finally, speakers switched to Taiwanese because of the association with locally-evolved items in a conversation.