A caisson for maritime works, consisting of a base (1) and at least one lateral wall (2) attached to the same and formed by a plurality of voussoirs (3). Within the same a main space (4) is defined, intended to receive granular material as ballast. The voussoirs (3) feature an upper side (5), a lower side (6) and lateral sides (7) and are arranged with the lateral sides (7) of adjacent voussoirs (3) attached to each other, forming horizontal segments (8). Said horizontal segments (8) are attached to other identical horizontal segments (8) to define the lateral wall (2) by means of the union of the lower sides (6) and upper sides (5) of the voussoirs (3) forming the same. The base (1) has a geometric shape which coincides with the geometric shape of the horizontal segments (8). A procedure for the assembly of said caisson for maritime works is also described.