As the core channels in Korea’s mobile messaging advertising market, traditional SMS advertising and the emerging format of Kakao Brand Messages have come to dominate the landscape. Despite their high effectiveness, mobile messaging ads can also provoke consumer resistance due to perceptions of intrusiveness and concerns about privacy. This study compares SMS advertising and Kakao Brand Messages to examine how perceptions of platform characteristics and advertising characteristics influence advertising effectiveness in mobile messaging contexts. Drawing on platform trust theory and the Technology Acceptance Model (TAM), we developed a set of hypotheses and tested them using data collected from 400 consumers aged 20 to 59 through a within-subject experimental design. Results from structural equation modeling indicate that Kakao Brand Messages were evaluated significantly more positively than SMS advertising in terms of reliability, security, and controllability. Perceived usefulness and perceived ease of use were also more favorable on the Kakao platform, whereas perceived risk was higher for SMS advertising. These differences in perceptions were further associated with advertising outcomes, including brand attitude, purchase intention, and recommendation intention. This study offers theoretical and practical implications for developing mobile marketing strategies.