Neptune is shown to be a calm, collected, and respectful individual with a carefree personality. He maintains a positive impression with people he meets and often hangs out with his friend Sun Wukong, who describes him as being cool. Neptune is prone to flirting with girls, as shown through his interactions with Yang Xiao Long, Weiss Schnee, and even Miltia and Melanie Malachite, despite having just met them at the time. However, he is only successful with Weiss.

He's shown to be fashion-conscious, like when he interjects that Sun doesn't know what he's talking about following the latter's claim that he can simply wear his casual clothes to the upcoming Beacon Dance.

Aside from fitting the stereotypical popular guy image, he may have an intellectual side as well as evidenced in the episode "Welcome to Beacon". When Sun says "Don't be a nerd", Neptune quickly corrects his friend, calling himself an "intellectual". This intellectual side of him shows through, when it is later mentioned that he defeated Ruby Rose Weiss, and Yang in a round of Remnant: The Game off-screen.

Despite his cool demeanor, Neptune is very self-conscious of his image and can be easily embarrassed over his minor inadequacies, like his inability to dance, and refused to admit his fear of water. His tendency to protect his reputation can sometimes make him inconsiderate to the feelings of others.

Neptune has a couple contradictory nervous tics. When Ruby forces him to be Yang's partner, taking hold of him and moving him where she wanted him to stand, he becomes stiff as a board. This same behavior is seen when Neptune notices the ocean biome in "New_Challengers...". However, when Jaune talks to Neptune about his refusal to go to the dance with Weiss, instead of becoming stiff, Neptune becomes restless, rubbing the back of his neck and looking away.

Neptune at one point was poor at keeping secrets. When Sun lets it slip that Blake Belladonna is a Faunus and wants to keep it secret, he mentions Neptune telling Scarlet David secrets in the past behind his back.