Containing device for containing and correctly holding a closed container (11) for fluid products inside a mixing machine (12) for said fluid products. The containing device comprises a container element (13) provided with at least a lateral wall (14) that defines a compartment (24), which is open and accessible from above, has a longitudinal axis (X) in the center and in which the container (11) is able to be disposed with play. Radial pressure elements (15) are disposed on substantially opposite sides with respect to the longitudinal axis (X) and are movable in synchrony in order to selectively clamp the container (11) in a central position inside the compartment (24).