A joining device between components of an item of furniture, comprising: - a casing extending along a longitudinal axis between a first end susceptible to being received in a first seat afforded in a first component of said item of furniture, and a second end susceptible to being received in a second component of said item of furniture, said casing comprising a first and a second portion which are radially expandable for engaging the components of the item of furniture at the first and at the second seat, respectively; - a tie-rod housed within the casing and axially slidable from a rest position, in which the said radially expandable portions, are retracted, to a locking position in which said radially expandable portions, are expanded outside the dimensions of the casing; said tie-rod having a first, and a second enlargement respectively at said first and second radially expandable portion so as to perform the expansion of said portions; said tie-rod comprising a head arranged at one end of the tie-rod itself opposite the first and the second enlargement; - at least one cam element housed in said casing and operatively associated with an abutment portion of said tie-rod for axially moving the latter from the rest position to the locking position and vice versa when said cam element is turned about its own axis of rotation that is transversal with respect to the axis of the tie-rod; characterised in that said cam element has a lobe along its outer periphery, which has a forward profile having a predefined extension about the axis of rotation such as to perform, alone, the displacement of the tie-rod with respect to the casing from the rest position to the locking position so as to actuate the expansion of both portions, with a single movement according to a forward rotation direction of the cam element; said abutment portion of the tie-rod being arranged at said head and rises in relief on said head so as to enter into interference with the cam element for realising said displacement of the tie-rod. - a casing extending along a longitudinal axis between a first end susceptible to being received in a first seat afforded in a first component of said item of furniture, and a second end susceptible to being received in a second component of said item of furniture, said casing comprising a first and a second portion which are radially expandable for engaging the components of the item of furniture at the first and at the second seat, respectively; - a tie-rod housed within the casing and axially slidable from a rest position, in which the said radially expandable portions, are retracted, to a locking position in which said radially expandable portions, are expanded outside the dimensions of the casing; said tie-rod having a first, and a second enlargement respectively at said first and second radially expandable portion so as to perform the expansion of said portions; said tie-rod comprising a head arranged at one end of the tie-rod itself opposite the first and the second enlargement; - at least one cam element housed in said casing and operatively associated with an abutment portion of said tie-rod for axially moving the latter from the rest position to the locking position and vice versa when said cam element is turned about its own axis of rotation that is transversal with respect to the axis of the tie-rod;