We examined cognate effects when late fluent Spanish/English bilingual speakers undergoing event-related potential recordings performed two tasks on word pairs. In an association decision task, participants decided whether or not pairs of Spanish words were related in meaning. In a translation decision task, they reported whether English target words were correct translations of Spanish primes. In both the tasks, word primes were either cognates or noncognates. In the translation decision task, faster and more accurate responses were associated with reduced N400 amplitudes in word pairs featuring a cognate. However, cognates did not modulate performance or event-related potentials in the association decision task. The results suggest that language coactivation in bilingual speakers is modulated by cognitive context.