Dishonest behavior often occurs in groups where actions are interconnected and beliefs about others' behavior may play an important role. We study the relationship between beliefs and dishonesty, focusing on the impact of the nature of the strategic interaction (complements or substitutes) and the reduced feeling of responsibility that arises from acting together with other group members. In settings of strategic complements, we observe that individuals tend to lie more, the more they believe their counterpart to be dishonest. Conversely, in settings of strategic substitutes, individuals tend to lie less as their belief about their counterpart's dishonesty increases. Acting together instead of acting alone-while holding the nature of the strategic interaction and beliefs constant-does not influence the relationship between beliefs and behavior in strategic complements. However, individuals with higher lying costs lie less in strategic substitutes when they are the only active member of the group. Our findings suggest that both beliefs and the type of strategic interaction strongly shape group dishonesty, while responsibility plays a minor role.