Neptune is normally associated with Pisces, glamours, the arts, loss, confusion, dreams, fantasies, lies and deception, storytelling, media, heightened inspirations, deep water, underground fluids like oil, mass consciousness, drugs, alcohol, heightened emotional sensitivity, and lack of personal boundaries.

In a person's chart, Neptune aligned with their Sun may mean a loss of a sense of self-identity. This can manifest as a loss of commitment to one's vocation and/or avocation (hobbies) and even personal relationships and assets. Not all of these need to occur, but any and all of them can.

Neptune's positive manifestations can include:
- those attitudes and activities that are nonessential to living that the person has been attached to can fall away due to lack of interest and attention. This can clear the way for new relationships and activities and potential opportunities for the person.
- the person under this influence can seem quietly ethereal and magnetic, and lucky events may occur to them.
- the person's heightened emotional sensitivity can make them very empathic towards others' needs and sufferings. At least the person can relate better with others on a deep level - they may be seen as quite intuitive.
- if the person has not been accustomed to it, as in the case of a workaholic, the person may find themselves enjoying relaxing times in front of a TV, or having social drinks, or watching live art performances such as concerts, dance, and the like.
- the person would more greatly enjoy trips to the ocean, and spending time in the water generally. Long swims in the sea are a great way to witness the action of Neptune on us - since the sea is always moving, seems limitless, has its own profound character, can make us feel vulnerable and close to death, and can make us feel a part of the sea when we relax into it.
- the person can feel divinely inspired to serve humanity from time to time.
- because the person can lose touch with reality easily, the person gets to practice deliberately getting in touch with reality - both mentally, emotionally, and physically. By forcing themselves to think and act realistically, they save themselves much trouble, pain, and loss. This skill, when well practiced, will carry them forward for the rest of their lives, and can produce great success for them later on when Neptune's influence has passed.

Neptune's negative manifestations can include:
- suffering from the difficult emotions of others. Because the person's emotional sensitivities are heightened, it can be difficult for the person to distinguish their own emotions from others'.
- reflecting back on the attitudes and relationships and activities that were once dearly loved but have been released, the person can feel a real sense of the loss of self and the loss of a sense of personal purpose. This can be quite disconcerting and disillusioning.
- the person can indulge in drugs, alcohol, or other physical weakeners to their detriment.
- the person can lose themselves in games, TV shows, movies, or other distractions and lose sight of their essential activities and relationships, causing further personal loss and pain.
- the person can find themselves mingling with and attaching themselves to deceptive people who may not have the person's interests at heart. If these people engage in destructive practices, and induce the person to participate in them, it can cause the person a great deal of difficulty, pain, and loss. Oftentimes, the effects of these relationships will become clear only after Neptune's influence has waned, causing great personal consternation.