Penelitian ini bertujuan untuk menganalisis pengaruh integrasi pendekatan Social Scientific Issues (SSI) dengan model Project Based Learning (PjBL) terhadap hasil belajar siswa pada materi laju reaksi. Penelitian menggunakan metode quasi eksperimen dengan desain two group pretest–posttest. Populasi penelitian adalah siswa kelas XI IPA MAN 3 Medan, dengan sampel dua kelas yang dipilih secara purposive, yaitu kelas eksperimen dan kelas kontrol, masing-masing berjumlah 30 siswa. Instrumen yang digunakan berupa tes pilihan ganda sebanyak 20 soal yang telah divalidasi. Data dianalisis menggunakan uji normalitas, homogenitas, uji-t, dan uji N-gain. Hasil penelitian menunjukkan bahwa data berdistribusi normal dan homogen. Uji hipotesis menunjukkan nilai thitung (2,708) lebih besar daripada ttabel (1,671) pada taraf signifikansi 0,05, sehingga terdapat pengaruh signifikan penggunaan pendekatan SSI dengan model PjBL terhadap hasil belajar siswa. Selain itu, nilai N-gain kelas eksperimen (0,68) lebih tinggi dibandingkan kelas kontrol (0,64), yang keduanya berada pada kategori sedang. Temuan ini menunjukkan bahwa integrasi SSI dalam PjBL efektif dalam meningkatkan hasil belajar siswa serta mendorong keterlibatan aktif, berpikir kritis, dan kemampuan mengaitkan konsep kimia dengan isu sosial. Dengan demikian, pendekatan ini layak diterapkan sebagai alternatif pembelajaran kimia yang kontekstual dan bermakna. The Effect of the Social Scientific Issue Approach with the Project Based Learning Model to Improve Student Learning Outcomes This study aims to analyze the effect of integrating the Social Scientific Issues (SSI) approach with the Project-Based Learning (PjBL) model on students’ learning outcomes in reaction rate material. The study employed a quasi-experimental method with a two-group pretest–posttest design. The population consisted of eleventh-grade science students at MAN 3 Medan, with two classes selected through purposive sampling as the experimental and control groups, each comprising 30 students. The research instrument was a 20-item multiple-choice test that had been validated. Data were analyzed using normality, homogeneity, t-test, and N-gain tests. The results showed that the data were normally distributed and homogeneous. The hypothesis testing revealed that the t-value (2.708) was higher than the t-table value (1.671) at a significance level of 0.05, indicating a significant effect of the SSI approach integrated with the PjBL model on students’ learning outcomes. Additionally, the N-gain score of the experimental class (0.68) was higher than that of the control class (0.64), both categorized as moderate improvement. These findings indicate that integrating SSI into PjBL is effective in improving students’ learning outcomes, promoting active engagement, critical thinking, and the ability to relate chemical concepts to real-world social issues. Therefore, this approach is recommended as a contextual and meaningful alternative for chemistry learning.