In recent years, studies on technological, pedagogical, and content knowledge (TPACK) have been increasing; however, integrating TPACK into online teaching has generated concerns among teachers across various subject domains in the humanities. Since there have been few recent reviews of teachers' online TPACK research in the humanities, the present study systematically reviews research in this area published between January 2012 and June 2022. This review aims to advance the knowledge on using TPACK in different subject disciplines while providing practical implications for technology integration in online teaching. The review of 24 articles revealed article frequency reached a peak in 2021 and 2022 covering various subject domains in the humanities. Most studies collected data through qualitative methods while focusing on in-service teachers. The articles were categorized into three research areas: exploring, measuring, and applying TPACK. Among the disciplines, the results showed that language teachers had various TPACK competencies in online teaching; journalism teachers' collaborations during online course delivery were facilitated when integrating TPACK; and music teachers' individual beliefs for online teaching were predicted by TPACK. The reviewed research used TPACK as the theoretical basis for scale development to assess teachers' readiness for flipped teaching. The reviewed articles indicated that TPACK was helpful for language teachers' technology integration as well as course and platform design during their online teaching.