Moral rules are rigid. The 10 Commandments of the Bible’s Old Testament, for example, include unambiguous prohibitions, such as, “Thou shalt not kill.” Similarly, Kant’s categorical imperative is absolute: “Act only in accordance with that maxim through which you can at the same time will that it become a universal law” (Kant, 1785/2002; emphasis added). In practice, however, people often struggle to determine what is right or wrong. Consider a doctor treating a terminally ill patient who is suffering from unrelenting pain. She may struggle to decide whether the right course of action is to honor the Hippocratic Oath (not to mention laws that explicitly forbid euthanasia in most states) or honor the patient’s request to provide drugs he can use to end his life, especially if the doctor believes that she would make the same request if she were in the patient’s position. She therefore faces a dilemma because multiple moral principles produce conflicting mandates. Decisions that involve tension between moral principles can generate cognitive conflict within a person and ignite disagreement between people. Ultimately, small variations in context across situations can tip the balance between competing moral forces and lead to principle-inconsistent decisions. Our focus in this essay is moral flexibility, a term that we use to capture to the thesis that people are strongly motivated to adhere to and affirm their moral beliefs in their judgments and choices — they really want to get it right, they really want to do the right thing — but context strongly influences which moral beliefs are brought to bear in a given situation (cf. Bartels, 2008). In what follows, we review contemporary research on moral judgment and decision making and suggest ways that the major themes in the literature relate to the notion of moral flexibility. First, we take a step back and explain what makes moral judgment and decision making unique. We then review three major research themes and their explananda: (i) morally prohibited value tradeoffs in decision making, (ii) rules, reason, and emotion in tradeoffs, and (iii) judgments of moral blame and punishment. We conclude by commenting on methodological desiderata and presenting understudied areas of inquiry. We acknowledge that this chapter provides an incomplete view of the literature on moral psychology. We focus on moral judgment and decision making in situations that involve tension between moral principles. This focus reflects the intense theoretical curiosity these situations have garnered from behavioral scientists. We do not review one common type of moral choices people face — those that involve tension between moral principles and (material) self-interest — because they are (arguably) less perplexing for models of decision making than situations where moral principles are in conflict. Given our focus on moral judgment and choice, we also do not review research on (im)moral behavior (e.g., stealing, cheating, charitable giving, helping; for reviews see Tenbrunsel & Smith-Crowe, 2008; Treviño, Weaver, & Reynolds, 2006), research on the correspondence between moral behaviors (as in moral licensing; see Merritt, Effron, & Monin, 2010; Sachdeva, Iliev, & Medin, 2009), or research on the correspondence between moral principles and behavior (as in moral hypocrisy; see Monin & Merritt, 2012; Tenbrunsel, Diekmann, Wade-Benzoni, & Bazerman, 2010). Each of these omitted areas of research, as well as others we have not mentioned, illuminate features of morality that are worthy of further review (for broader treatments of morality see edited volumes by Bartels, Bauman, Skitka, and Medin, 2009; Sinnott-Armstrong, 2008, Vol 1, 2, 3).