A machine for packaging fiber material comprises feed means (2) supplying predetermined portions of fiber material (3) in an ordered succession, compacting means (4) by which the portions of fiber material (3) are compacted initially, a feed station (8) to which packs (9) are supplied for filling with the fiber material (3), a filling station (D) at which the fiber material (3) is inserted into the packs (9), and a closure station (E) located downstream of the filling station (D), at which the filled packs (9) are sealed. The machine further comprises fiber material (3) compressing and forming means (7) by which each of the portions of fiber material (3) is maintained in a state of compression downstream of the compacting means (4) for a prescribed interval of time, in such a way that the selfsame portion of fiber material (3) is caused to assume a compact geometry of tablet-like form prior to its insertion into the respective pack (9).