Learning chemistry may be difficult for students for several reasons, such as the abstract nature of many chemistry concepts and the fact that students may view chemistry as irrelevant to their everyday lives. Teaching chemistry in familiar contexts and the use of multiple representations are seen as effective approaches for enhancing students' conceptual understanding and attitudes toward science. This study, therefore, explored the effects of chemistry instruction incorporating the multiple levels of representation (MLR) approach in the context of household chemistry on students' understanding and attitude toward science. Participating students were 49 Grade 7 Thai students from a secondary school in Songkhla province, Thailand. A quasi-experimental, one-group pre-test/post-test design was used to assess students' learning gain, achievement levels, and attitude toward science. Research instruments consisted of the Test of Logical Thinking (TOLT), an achievement test on basic household chemistry, and the Test of Science Related Attitudes (TOSRA). Results indicated that among the 49 participants, 19, 15, and 15 students were identified as concrete, transitional, and formal in terms of their cognitive development levels, respectively. Results of a Wilcoxon signed-rank test indicated that post-test scores of all groups were higher than the pre-test at the 0.01 level of statistical significance. In addition, the average learning gain of the concrete, transitional, and formal students were 21%, 21% and 29%, respectively. The analysis of t-test for one sample revealed that after learning with the Chemistry Learning Material--Multiple Levels of Representation (CLM-MLR) approach, the students had a high attitude towards science overall. Level of students' cognitive development that affects learning outcomes with the multiple representation approach is discussed.