Initially, Flowey operates under a façade of friendliness and politeness. He often greets the protagonist with southern slang, such as "Howdy!", calls himself "your best friend," and, like his father, appends polite words such as "gosh" and "golly" to the ends of his sentences. Whenever he drops this guise of friendliness, he often calls the protagonist an "idiot."

Flowey has a malevolent and cruel disposition, berating the protagonist for not following his "kill or be killed" philosophy. Despite this, he also criticizes the protagonist at the end of the Ruins if they killed any monster. He is manipulative, devious, and a cunning planner and subtle if the circumstances require it. He retains his memories between SAVEs because he was once able to SAVE. He is also shown to be extremely cowardly, as he kills his former father to appease the protagonist in a vain attempt to save his own life in the Genocide Route's conclusion.

Before his death, Asriel was a docile, unadventurous, and loving child. He cared for the First Human as a sibling, and he trusted them when they came up with a plan to escape the Underground that involved them consuming buttercups.

After Alphys resurrects Asriel without a SOUL as Flowey, he becomes incapable of feeling love. This makes him bored and resentful. After temporarily regaining his compassion, he apologizes for his actions to Frisk and realizes the gravity of his actions as a flower.