This phenomenographical study examined 10 American science, technology, engineering, and mathematics (STEM) teacher leaders' (TL) conceptions of and activities in STEM education advocacy before and during the coronavirus disease 2019 (COVID-19) pandemic. Data collection consisted of semi-structured interviews conducted via online conferencing before the onset of the pandemic and responses to an online questionnaire completed during the pandemic. The outcome space emerging from the participants' conceptions of STEM education advocacy were: (1) identity, (2) communication, and (3) movement. Communication was a priority of advocacy activities before COVID-19 interruptions, whereas movement was thematically transformed due to participants' experiences (challenges and successes) in transferring their advocacy activities to online modalities. This study addresses gaps in STEM teacher and teacher advocacy literature by qualifying TLs' conceptions of and activities in education advocacy.