The state of New Jersey has not updated their standards and requirements for teachers' professional development since 2014 and COVID-19 has changed the landscape of education drastically. The aim of this mixed-grounded theory study was to see if the events of COVID-19 had an effect on K-12 New Jersey public school teachers' perceptions of online professional development as well as their self-efficacy based on these perceptions. A quantitative survey was administered remotely to public school teachers from across New Jersey (n = 279), then qualitative semi-structured follow up interviews were conducted to further explore the quantitative results (n = 13). The interval survey data was analyzed using the descriptive statistics mean, median, mode, and standard deviation as well as comparing the individual before and after responses. The interview transcripts were analyzed through three stages of coding, which included open, focused, and theoretical. Quantitative findings showed that 94.26% of teachers reported one or more changes to their perceptions of online professional development after the advent of COVID-19, though the median and mode responses changed in only 4 of the 11 question pairs. The qualitative findings revealed that teachers' experiences of and perceptions of online professional development were connected across the themes of money, disconnect, stress, convenience, peer interaction/collaboration, and effectiveness. These six themes were then grounded to the four concepts of Self-efficacy Theory and looked at in combination with the survey data in order to determine if these perceptions impacted teachers' self-efficacy. Through this analysis, the researcher determined that the events of COVID-19 did have an impact on teachers' perceptions of online professional development and their self-efficacy. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]