The current study was conducted to fill a gap in the literature regarding online instruction in K-12 settings in Saudi Arabia during the COVID-19 pandemic. Specifically, it aimed at gaining an understanding of the attitudes of teachers in Saudi Arabia towards online instruction and their readiness towards its implementation. It also sought to determine the teachers' perceived effectiveness of online instruction and the challenges they encountered in the Saudi K-12 context. An online survey was adapted to measure four scales: (a) attitudes toward online instruction, (b) the perceived effectiveness of online instruction, (c) the perceived readiness to implement online instruction, and (d) challenges of online instruction. The participants consisted of 584 teachers in the Saudi K-12 context who taught online during the COVID-19 pandemic, with varying years of teaching experience and training to teach online. The results of the survey were analyzed using a quantitative descriptive method. The findings indicate that Saudi K-12 teachers had a general positive attitude towards online instruction. It also revealed the teachers' readiness to implement online instruction despite the lack of training and previous online teaching experience. However, the Saudi teachers implied that they were undecided about the effectiveness of online instruction, especially when compared to in-person instruction. Implications and recommendations were proposed based on the results of the study, in addition to suggestions for future research regarding online instruction in K-12 settings in Saudi Arabia. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]