The objective of this research was to find out the effectiveness of STEM-based student worksheets to improve data literacy. The research method used is in the form of Quasi-experimental research design with the One-Group Pretest-Posttest. Students of class XI MIPA 2 in MAN 2 Yogyakarta were the subjects of this research. The data analysis included the results of the pretest, posttest, N-Gain test and non-parametric statistical tests to determine the increase in student data literacy descriptively. Based on the findings of the data analysis, it was achieved: 1) there was an increase in the value of data literacy taught using STEM-based student worksheets with N-Gain of 71% in the high category; and 2) STEM-based student worksheets are effective for improving participant data literacy by obtaining sig values. equal to 0.000 which is smaller than α = 0.005