Having experienced nothing like a normal, complete childhood, Phoebe is often quite naive and innocent, and is in some regards still a child at heart. She still believes Santa Claus existed (until Joey tells her otherwise). She is also overjoyed when Ross gets her a pink bicycle (with ribbons tied to the handles) after she tells the gang she never had a bike as a child, let alone knew how to ride one, due to her family's hardships. One of her goals by the time she was 30 was to have gone one mile while bouncing on a Hippity Hop.

Phoebe appears to be the most "promiscuous" of the three girls, being the one most often referred to as having casual sex. It was hinted at several times during the show that Phoebe enjoyed 'kinky' sex, involving, for example, handcuffs. At one point, she suggests Mike's absence was due to her having handcuffed him to a drainpipe. She also alludes to having had sex in an elevator and in a public restroom. In a later episode, she is apparently trying to convince Mike to do something very weird and/or kinky, and whispers her wish to Joey, he is clearly disturbed and leaves, yelling "I'm not helping you do that!". During the episode The One with Rachel's Phone Number, Rachel attempts to convince Mike to do her a favor by promising that Phoebe will do anything he wants: "Seriously, I'm talking dirty stuff." Mike is surprised that it could "get any dirtier". In an episode where she wants to know more about a man and sends Joey to ask him questions, she is disappointed to learn that he "isn't into weird stuff - sexually". In Season 3 Episode 11 (The One Where Chandler Can't Remember Which Sister), she is sent to yell at the noisy man that lives upstairs from Rachel and Monica, but starts dating him, and Monica and Rachel hear sexual noises through the ceiling a couple of days later.

Phoebe often uses her chaotic childhood and traumatic past as sympathy ploys to her friends. References to her mother's death were usually to get her own way. However, as the series progressed, the other friends indulge her less frequently. The irony is that both Phoebe's biological parents are still alive and well, so she actually does have a complete family (albeit a broken one).

Although regarded by many as a stereotypically flaky "New Age" type, Phoebe's actual religious faith is somewhat vague. She deeply believes in reincarnation and referes to multiple gods (including Lucifer and the Norse gods Thor and Odin), which would seem to make her a Pagan; however, not all of Phoebe's beliefs seem internally connected, and it is probable that she has picked up tidbits from a number of religions and simply woven them into her own unique faith, apparently prompting her belief her grandmother is in hell. She is very open to the existence of paranormal phenomena and willing to consider the most bizarre scientific theories, much to Ross' confusion and despair. She, however, does not believe the theory of evolution (The One Where Heckles Dies) or even that of gravity, claiming she feels more pushed down than pulled. At one point, Phoebe is even possessed by the spirit of an 82 year-old woman who had unfinished business ("she wanted to see everything"), who departs when Phoebe attends a lesbian wedding. Phoebe also claims to hear voices in her head, and at one point, even heard Joey singing in his head. She also has a tendency to know what the other friends are up to. For example, when the gang get back from London, she announces that 'You ate meat' pointing at Joey and 'You had sex' pointing at Chandler and Monica.