Need for Closure (NFC) refers to an individual’s aversion to uncertainty and desire to quickly resolve it. Although numerous studies have demonstrated that this need leads to a reluctance to invest effort in judgments and decision making, we argue that NFC may be associated with less or more effort investment depending on key features of the performance situation and instrumentality of effort for achieving closure. Specifically, we expect that high (vs. low) NFC individuals should exert less effort when both lowand high-effort performance options are available and both afford closure. By contrast, they should exert more effort when task-related uncertainty causes that only effortful means are instrumental for the goal of achieving closure. If only a high-performance option allows the task goal to be attained and instructions how to perform a task are clear and specific, there will be no differences between high and low NFC participants. We tested these hypotheses in an experiment framed in terms of Motivational Intensity Theory. The experiment asked participants to solve cognitive tasks under relevant performance circumstances, indexing effort through assessment of systolic blood pressure (SBP) responses. Results were supportive. They help to account for contradictory findings in the NFC literature and add substantively to the broader literature concerned with determinants and cardiovascular correlates of effort.