Scientific argumentation is an essential part of science instruction. The 2013 curriculum that places scientific inquiry as an instructional approach and scientific literacy as a learning outcome is very concerned with scientific argumentation. Scientific argumentation is a statement supported by evidence and justified by relevant assumptions, principles, or concepts. The knowledge structure of salt hydrolysis includes scientific knowledge and scientific inquiry, including scientific argumentation. One of the inquiry-based instructions designed to improve students’ scientific inquiry abilities, including scientific argumentation, is explicit scientific inquiry instruction (ESII). This study aims to investigate the impact of the ESI instructional model on students’ scientific argumentation skills in salt hydrolysis. This study applied a one-group pre-test post-test design. The treatment variable was the instruction that applied the ESII, while the measurement variable was the scientific argumentation skills on salt hydrolysis. The subjects of this study were 64 students of 11th grade of SMAN 2 Malang, a public senior high school. The improvement of students’ scientific argumentation skills was analyzed using normalized gain scores and Cohen’s d-effect size methods based on the students’ pretest-posttest scores. The results showed that students’ scientific argumentation skills significantly improved with a Cohen’s d-effect size of 3.10 (much larger than typical) and the normalized gain score of 0.42 (medium). Students’ scientific argumentation skills in salt hydrolysis shifted significantly from low to medium category. This paper proves that inquiry-based instruction, in which the learning experiences are explicit for students, is effective in improving students’ scientific argumentation skills.