Important choices in life often have uncertain outcomes. Thus, it is important to understand the mechanisms that support decision making under uncertainty. Experimental work has shown that individuals’ attitudes towards risk and ambiguity are related to decision making, and that information about others’ choices can influence individuals’ decisions. However, it is currently unknown how information about others’ choices influences risk and ambiguity attitudes, and the degree to which others’ choices shape decision making differentially across development from adolescence to young adulthood. The current study used a computational modeling framework to test how information about others’ choices influences these attitudes. Participants, aged 14-22 years old, made a series of risky and ambiguous choices while undergoing fMRI scanning. On some trials, they viewed the previously risky or safe choices of others. Results showed that participants aligned their choices toward the choice preferences of others. Moreover, the tendency to align choices was expressed in changes in risk attitude, but not ambiguity attitude. The change in risk attitude to align with peers was positively related to neural activation in the medial prefrontal cortex, an area known for its integrative role of different sources of information during decision making. Results did not show age-related differences in behavior and corresponding neural activation, indicating that adolescents and young adults employ similar processes when incorporating social information into their decisions.