Cognitive control involves the allocation of cognitive resources in order to successfully navigate and interact with the world. Oftentimes, control involves balancing the demands brought on by performing immediately relevant tasks and those required in order to perform future intended actions. For example, directing attention towards navigating through traffic on a highway while also needing to remember to exit the freeway at a particular street. This ability to delay execution of a goal until the appropriate time in the future is referred to as prospective memory (PM). The dual mechanisms of cognitive control (DMC) framework posits that individuals can use two different strategies to remember an intended action: a proactive control strategy involving working memory maintenance of the goal and monitoring of the environment, or a reactive control strategy relying on timely retrieval of goal information from episodic memory. Previous research on prospective memory has demonstrated that performance improves when individuals engage these control strategies in accordance with the demands of the task environment. However, it is unclear how people select a control strategy, particularly in situations with dynamic task demands. We hypothesized that if people flexibly adapt their strategy in response to changes in the environment, this should facilitate prospective memory. Across two experiments, we asked participants to identify the reappearance of a picture target (a prospective memory intention) while at the same time performing an ongoing visual search task. The attentional demands of the ongoing task were manipulated to monotonically increase or decrease on a moment to moment basis. The selection of control strategies was identified using reaction time costs and neural measures of intention maintenance. Results showed that people fluidly modified control strategies, shifting towards proactive control when the attentional demands decreased, and shifting towards reactive control when attentional demands increased. Critically, these adaptive shifts in control strategy were associated with better prospective memory performance. These results demonstrate that fine-grained control of attention and memory resources serves an adaptive role for remembering to carry out future plans.