A modular mattress comprising a plurality of modules configured to be positioned adjacent to each other forming a unique body having a support surface for a user, and comprising a plurality of engagement elements configured to reversibly engage a first and a second module of said plurality of modules, for avoiding movement from a correct relative position. The plurality of modules comprises a group of modules providing respective through holes aligned and oriented along a first predetermined direction, said aligned through holes being arranged to form a passageway passing through said modules of each group. There is one connection element configured to be positioned within said passageway, each connection element being provided at opposite ends, with respective engagement elements for reversibly engaging with respective engagement elements of a first and a second end module positioned, respectively, at opposite sides of each group of modules.