The use of hashtags has become an effective tool for activists to mobilize public support. This study explores whether, and in what ways, such hashtags have been adopted by politicians in power. Conducting a systematic, cross-national analysis, we examine how politicians use, what we call, activism-related hashtags. Using data from the Twitter Parliamentarian Database, we analyze the hashtagging practices of politicians in 10 countries: Australia, Denmark, France, Germany, Italy, Norway, Spain, Sweden, the United Kingdom, and the United States. The analysis explores what types of hashtags politicians use, and to what extent these tags are activism-related. We also analyze what activist causes hashtags used by politicians are related to, to better understand what causes are the most palatable to politicians. We further analyze qualitatively how the activism-related hashtags are used by the politicians. Through a combination of thematic analysis and frame analysis, we find that, in relation to the wide range of hashtags that politicians use, activism-related hashtags constitute a limited share. Our analysis also indicates that although politicians do indeed use activism-related hashtags, this can be for many different reasons and purposes, beyond merely supporting the cause or position of the original activist initiative. We find that politicians may join in with the key contention behind the hashtag, renegotiate the meaning of the hashtag to be able to align party-political ideologies with it, or engage with it by questioning or subverting it.