The purpose of this study was to analyze the politeness strategies used in YouTube reaction vlogs and how these influence viewers. Content analysis was employed in identifying the politeness strategies used in the vlogs using Brown and Levinson's politeness theory. The results showed that there were 231 polite utterances used. The frequently used politeness strategy was positive politeness (48.05%), followed by bald on-record politeness (25.11%), off-record politeness (13.85%), and negative politeness (12.99%). A phenomenological inquiry was employed to gain the insights of 14 educators as participants in in-depth interviews and focus group discussions on how politeness strategies in reaction vlogs influence viewers. The following themes emerged: make a good conversant, give respect and protect an image, train how to evaluate issues and reactions, learn to appreciate vlogs, and aid in the teaching-learning process. Reaction vlogs, as an investigative genre of vlogging, could become a springboard to teach politeness and politeness theory and supplementary materials in teaching. Reaction vlogging, as a form of self-expression, could serve as a performance task among learners.