Mould and method for realizing a temporary prosthesis of hip or shoulder, which comprises a shaft and a head. The mould comprises: a first mould portion (1) comprising a first half-shell (2); a second mould portion (3) comprising a second half-shell (4); the first mould portion (1) and the second mould portion (3) being able to be coupled with respect to each other so that the first and second half-shell (2, 4) are counter-faced and define a chamber (5) which conforms a shaft portion (5a), a head portion (5b) and an opening (5c) for injection of a fluid (preferably viscous) material; fixing means (6) for fixing the first and the second portion (1, 3); a first insert (7) comprising a cap portion (8) which is realized as a unique body, is dimensioned to be inserted in the head portion (5b) and is conformed to give shape to the head of the prosthesis. The first mould portion (1), the second mould portion (3) and the first insert (7) are mutually conformed to obtain a temporary prosthesis, when the first mould portion (1) and the second mould portion (3) are coupled together, the first insert (7) is inserted in the head portion (5b) and the fluid (preferably viscous) material is injected in the opening (5c).