The COVID-19 outbreak has suddenly changed the landscape of education worldwide. Many governments have moved education completely online, with the idea that although schools are shut, classes can continue; however, the question regarding whether teachers are prepared for this massive shift in educational practice remains unanswered. This study addresses this issue through the lens of teachers’ technology, learners, pedagogy, academic discipline content, and content knowledge (TLPACK). Two groups of 250 teachers (n = 500) who teach various levels of students participated in a two-phase survey. The phases of the survey took place in 2017 and 2020 (i.e., before and during the COVID-19 pandemic). Participants answered 38 reliable and valid questions about TLPACK to address three research questions, and the collected data were subjected to frequentist and Bayesian statistical analysis. The analysis indicated that teachers’ TLPACKs were significantly different before and during the COVID-19 pandemic. This study revealed significant correlations among teachers’ TLPACK constructs and found that, among these constructs, the strongest relationship was that between learner knowledge (i.e., knowledge about the learners) and pedagogy knowledge. The study ends by reflecting on our findings’ implications, especially since the COVID-19 pandemic continues to have significant altering effects on both education and society at large.