This paper reports helpful notes to teach pronunciation to Korean learners of Vietnamese. Based on comparing the similarities and differences in vowels and consonants system between the Korean language (L1) and the Vietnamese language (L2) and showing the knowledge of L2 phonetics and phonology, as well as accumulating experience of teaching Vietnamese to Korean learners for many years in both Vietnam and Korea, the paper (i) points out the errors of pronunciation of Vietnamese that Korean learners are likely to make; (ii) examines and analyses the causes of this mispronunciation carefully; and (iii) suggests the solutions to avoid and overcome this mispronunciation. In addition, the methodologies and activities of teaching pronunciation are presented in order to help Korean learners pronounce Vietnamese accurately and avoid potential errors.