Increasing evidence suggests that higher-order thalamic nuclei are implicated in cognitive behavior. Unlike those in the first-order thalamus, higher-order thalamic neurons have a high propensity to switch from tonic spiking to rapid spike sequences termed bursts. Although bursts have been linked to the augmentation of information transfer in a manner that may support behavior, their role in cognition has never been tested. We show that bursts in the pulvinar, a thalamic node linked to cortical coordination during attention, are attention-modulated and predict behavior. Using neural data from the pulvinar and parietal cortex in macaques performing an attention task, we found that pulvinar bursts were predictive of target detection and reconfigured population codes of spatial location in cortex. Electrical microstimulation of the pulvinar triggered bursts that enhanced target detection and synchronized cortical spiking. These results establish pulvinar bursts as a causal driver of attention, revealing a mechanism by which the higher-order thalamus exerts control over cortical processing and behavior.