Teaching ethics in elementary science may seem abstract or simply another topic to add to an already rigorous curriculum. However, it is an integral part of science and engineering instruction and a natural extension of what elementary educators do every day. Teachers help students develop ethical practices or "habits of mind" when they: expect students to be honest, ask students to write persuasive essays to support a position about the "right" thing to do, or have students analyze the actions of a character in a story. Habits of mind are practiced ways of thinking and doing (Rutherford and Ahlgren 1990). In this article, the authors share how they have included ethics within a science-integrated engineering unit in a fourth-grade class. In this environmental engineering unit, students designed a process to clean an oil spill within a model ecosystem. To infuse ethics into the unit, they: (1) engaged students in investigating and discussing real-world ethical dilemmas related to oil spills and ecosystems; and (2) developed five strategies to encourage students to consider, practice, and reflect upon their own ethical decisions related to data collection and analysis.