Memories of past experiences can guide our decisions. Thus, if memories are undermined or distorted, decision making should be affected. Nevertheless, little empirical research has been done to examine the role of memory in reinforcement decision-making. We hypothesized that if memories guide choices in a conditioning decision-making task, then manipulating these memories would result in a change of decision preferences to gain reward. We manipulated participants' memories by providing false feedback that their memory associations were wrong before they made decisions that could lead them to win money. Participants' memory ratings decreased significantly after receiving false feedback. More importantly, we found that false feedback led participants' decision bias to disappear after their memory associations were undermined. Our results suggest that reinforcement decision-making can be altered by false feedback on memories. The results are discussed using memory mechanisms such as spreading activation theories.