gullible

Easily deceived or duped; naive, easily cheated or fooled.

Andrew is so gullible, the way he still believes in Santa Claus, the Easter Bunny, the Tooth Fairy, and the Sandman at the age of fourteen.

A gullible person; someone easily fooled or tricked.

They pictured to these gullibles the unearthly delights that were to be enjoyed as servants of the Spaniards. But such tricks could not last, for Cuba was too close to Saint Domingue, and news of the real conditions leaked across the windward passage and were bruited about.

Spurious accounts that snare the gullible are readily available. Skeptical treatments are much harder to find.