This descriptive-correlational study aimed to ascertain the relationship of science and mathematics Grade Point Averages (GPA) to the National Career Assessment Examination (NCAE) scientific and mathematical abilities of the high school seniors in Romblon State College –Sibuyan Branch, in San Fernando, Romblon. The subjects of the study were the 42 high school seniors enrolled during school year 2007-2008. The data needed for this study were obtained through the use of Form 137 (Permanent Record) of the students and their NCAE results taken on August 28, 2007. The following statistical tests were utilized in this study: for descriptive statistics, the means and standard deviations were used, for inferential statistics, Wilcoxon Signed Rank Test, Linear Regression Analysis, and Spearman Rank Correlation Coefficient were used. The level of significance was set at alpha 0.05 for a two-tailed test. Findings of the study revealed that the senior high school students of Romblon State College- Sibuyan Branch, were very good in science but were only good in mathematics. Mathematics GPA can predict the performance of senior high school students in the NCAE Scientific Ability, and Mathematical Ability but not the NCAE GSA. Only the GPA in mathematics carried significant cross-subject benefit. Furthermore,the GPAs in science and mathematics can predict the performance of senior high school students in the NCAE Mathematical Ability. Likewise, the GPAs in science and mathematics mutually influence each other. Moreover, these GPAs have great effect on NCAE GSA, that is, high GPAs in science and mathematics would imply higher performance in NCAE GSA.