Dark personality traits have been linked to behaviors commonly understood as unethical, such as fraud, bribe-taking, and marital infidelity. Presumably, more "light" personality traits may be associated with lesser tendencies to be unethical, but many individuals also possess both light and dark trait characteristics. This paper reports results from a preregistered study of over 2400 participants who completed validated short-form personality instruments to assess dark and light personality trait measures—the dark tetrad and a light "triad" of 3 personality dimensions were measured. Furthermore, participants completed 3 tasks of interest that contribute to an understanding or one's ethics: a task assessing prosociality, a task that presents a monetary temptation to be dishonest, and a hypothetical moral dilemma task. The results overall support the hypotheses that dark personality traits predict lower levels of prosociality, higher likelihood of dishonesty, and an increased willingness to make immoral choices overall. Potential mechanisms and implications are examined.