What does it mean to dream about box?
A box tends to hold something hidden or kept back, so it helps to ask whether you wanted to open it and what you feared or hoped to find.
Four ways to read it
Each reading below comes from a named tradition and a cited source, so you can see where it came from and decide what fits your dream.
Freud
Freud would read a closed box as a container with bodily and secret meaning, what is shut away and longed for or dreaded. Opening it can express the wish to uncover what is hidden.
After Freud, The Interpretation of Dreams (Brill trans., 1913), public domain.Jung
Jung might see a box as the contents of the unconscious waiting to be opened, a part of the self held in reserve. What is inside, gift or trouble, can show what you are ready to face.
Jungian concept (our summary).Modern
Continuity ties boxes to waking thoughts about secrets, choices, and things put away or unresolved. A box you cannot open often echoes a matter you have not yet looked at squarely.
Continuity hypothesis (our summary).Mythological
The sealed box of myth, like Pandora's jar, holds what should not be loosed, and once opened cannot be closed again. The hidden container has long carried both temptation and warning.
Rosmerta Publishing editorial synthesis (after Bulfinch; Brewer).