This paper uses the question, "what ethical issues inform our response to nonindigenous invasive species?" as a basis to explore human relationships to nature in the context of teaching environmental ethics. While ecologists express increasing concern about the introduction of non-indigenous invasive species (NIS), the public is sometimes unaware of, or ambivalent about, the problems they cause. I argue that this ambivalence stems from conceptual problems—about human-nature relationships, about ethical conflict and about human behavior—that can be addressed in a course on environmental ethics. Such a course can look at NIS in the context of different ethical traditions, and the different bases for action (or not) with regard to NIS that such ethical traditions imply. I suggest ways to use NIS as case studies in either a science course or an environmental ethics course, to introduce fundamental questions and to explore basic worldviews with respect to humans and nature.