Penelitian ini bertujuan untuk mengetahui keefektifan model Think Pair Square (TPS) berbasis Guided Inquiry pada tema sistem transportasi terhadap peningkatan hasil belajar kognitif dan sikap ilmiah siswa, serta untuk mengetahui tanggapan siswa terhadap model pembelajaran tersebut.Jenis penelitian ini yaitu quasi experimentdengan desain non-equivalent control group design. Sampel penelitian ini diambil dengan teknik purposive sampling, kelas VIII G (kelas eksperimen) yang diberi perlakuan model TPS berbasis guided inquiry dan kelas VIII H (kelas kontrol) yang diberi perlakuan model TPS berbasis structured inquiry. Data diambil dengan metode tes(pre-test dan post-test), observasi (sikap ilmiah), dan angket (tanggapan tentang model dan penilaian diri). Uji hipotesis yang dipakai yaitu uji perbedaan dua rata-rata (hasil belajar kognitif dan sikap ilmiah).Hasil penelitian menunjukkan bahwa rerata hasil belajar (post-test)kelas eksperimen lebih tinggi dari kelas kontrol (78,80> 76,13). Nilai N-gain kedua kelas masing-masing meningkat sebesar 0,56 dan 0,48 (kategori sedang). Ketuntasan klasikal kelas eksperimen (96,88%) > kelas kontrol (90,32%). Dari uji hipotesis, diperoleh thitung> ttabel (1,704> 1,671). Rata-rata nilai sikap ilmiah kelas eksperimen (79,3) lebih tinggi darikelas kontrol (77,6). Dari uji hipotesis diperoleh phitung<α (0,044< 0,05).Tanggapan siswa tentang model TPSberbasis guided inquirydinyatakan efektif (80,78). Hasil penelitian tersebut menunjukkan bahwa model TPSberbasis guided inquirypada tema sistem transportasi efektif terhadap peningkatan hasil belajar kognitif dan sikap ilmiah siswa. The aim of this study was to examine the effectiveness of Guided Inquiry based Think Pair Square (TPS) on the chapter of transport system. This study was concerned on raisingstudents’ cognitive skill and scientific attitude, alsoon finding outof the students’ response. The type of this study was quasi experimental design, especially non-equivalent control group design.The samplesof this study wasgrade VIII G (experiment) and VII H (control) of SMPN 26 Semarang, taken with purpossive sampling method. The data was taken by test method (pre-test andpost-test), observation (scientific attitude), also questionnaire (students’ responses and self-assesment). The results showed that the average of experiment classis higher than the control ( (78,80 > 76.13). This result proved by the t-test which achieved tvalue> ttable (1.704> 1.671). The N-gain value of both classes were increased by 0.56 and 0.48 (medium category). The classical completeness of experimental (96.88%)> controls (90.32%). The average value of the scientific attitudesof experimental (79.3) and control (77.6). This result verified by the Mann-Whitney test which obtained pvalue<α (0.044 < 0.05).The students’ responses about Guided Inquiry based TPSwas effective (80.78). In conclusion, students in the experimental group had better cognitives skill of Transport system, and more positive attitude toward Guided Inquiry based TPS.