He visits Bath when Catherine Morland is staying there with the Allens. He establishes himself quickly as a flirt. When Isabella Thorpe becomes engaged to James Morland, Tilney continues to flirt with her, finding it fun to put a wedge between James and Isabella's relationship. His younger brother, Henry Tilney, even tells Frederick of their engagement, but Captain Tilney clearly does not care.
He does not return with the rest of his family when they all go to Northanger Abbey with Catherine. Instead he remains in Bath, and flirts even more with Isabella. The young lady has already realized that James Morland is nowhere near as rich as she would like a husband to be, so she flirts with Frederick constantly, hoping to snatch the young captain's affections. She breaks the engagement with James, prompting her ex-fiancé to send a heartbroken letter to Catherine to let her know of what has occurred. After some weeks, Isabella realizes that Frederick will not be snatched, as he is far too fickle and crafty for that.
- Henry Tilney: "I have very little to say for Frederick's motives, such as I believe them to have been. He has his vanities as well as Miss Thorpe, and the chief difference is, that, having a stronger head, they have not yet injured himself. If the effect of his behavior does not justify him with you, we had better not seek after the cause."
- Catherine Morland: "Then you do not suppose he ever really cared about her?"
- Henry Tilney: "I am persuaded that he never did."
- Catherine Morland: "And only made believe to do so for mischief's sake?"
- — Conversation about Frederick Tilney between Henry and Catherine[src]
He is described as dashing and heroic in battle. When Catherine Morland first sees him in Bath, she thinks him possibly more handsome than Henry Tilney, but her affections do not waver. To Catherine's mind, his taste and manners are inferior to his brother's, especially when she hears him openly protesting against dancing.