Theories of motivation suggest that when people receive information about costs and benefits whilst making decisions, can influence their choices. But, do people have a preference for seeking information about the effort or rewards of actions first when making effort-based decisions, and does this impact motivation? Here, participants made choices about whether to work and exert different levels of physical effort to obtain different magnitudes of reward, or whether to take a rest for low reward. Prior to those choices, they also had to decide which information they wanted to see first: how effortful, or rewarding, work would be. We found no overall preference for seeking reward or effort information first, but motivation did change when people saw reward or effort first. Seeking effort information first, both for people’s average tendency and choices on specific trials, was associated with reductions in the willingness to exert higher effort. Moreover, the tendency to prefer effort information first was associated with reduced vigorous exercise and higher levels of fatigue in everyday life. These findings highlight that preferences for seeking effort information may be a powerful bias that reduces people’s willingness to exert effort in the lab and in their everyday lives.