The aim of the study was to investigate the effect of the Common Knowledge Construction Model (CKCM) lesson sequence on grade 7 students' conceptual understanding of the "water pollution" topic. Within a pre-experimental (one group pre-test/post-test) research design, this study was conducted with 25 (12 females and 13 males) grade 7 students in a lower secondary school in the district of Yenisehir, Bursa, Turkey. To collect data, word association test (WAT), conceptual understanding test (CUT), and interviews were employed. After calculating the students' responses to the WAT and the CUT, their scores were imported into SPSS 15.0™ to run paired samples t test and descriptive analysis. Also, the interviewees' responses to principal interview questions were thematically analyzed in regard to their similarities and differences. The results of the study showed that the CKCM lesson sequence resulted in a better conceptual understanding of the "water pollution" topic. The current study recommends to employ the CKCM lesson sequence for different science topics and varied grades and courses.