<p>Final-year high school students continue to face challenges in transitioning to higher education, with limited time to make crucial career decisions. Career decision-making self-efficacy (CDMSE) is essential in this process; however, existing interventions often fail to reach all students, particularly in under-resourced contexts. This study addresses this gap by examining the effectiveness of STUDIA, a mobile-based career counseling application, in enhancing CDMSE among final-year students. Adopting a pre-experimental design, the study involved 30 students from a senior high school in Eastern Indonesia who participated in a six-week intervention. Data were collected using a 17-item CDMSE scale and analyzed through paired-sample t-tests using SPSS 27. The findings revealed a significant improvement in students’ CDMSE, particularly in the domains of self-assessment, goal selection, and planning. However, challenges persisted in the areas of occupational information and problem-solving. Differential impacts were observed across demographic groups, with urban students demonstrating greater gains than their rural counterparts, while both male and female students exhibited significant improvements. These results offer valuable implications for educators and policymakers in designing effective, context-sensitive school career counseling programs that incorporate technological tools to support students during the critical transition to higher education. Despite its promising results, this study highlights the need for future research with stronger designs, broader samples, and longer interventions to ensure more robust and generalizable outcomes.</p>