In a method and apparatus for mechanically fastening an absorbent undergarment during the initial manufacturing thereof, the undergarment is transported in a transport direction and folded longitudinally by a folding device such that first and second end regions of the undergarment are in generally opposed relationship with each other while transporting the partially assembled garment in the transport direction to fastenably engaged first and second fastening portions of the undergarment. A central region of the absorbent undergarment is held by a holding device, separate from the folding device, against bunching between the end regions of the undergarment during longitudinal folding of the undergarment. In another embodiment, the transverse position of the second fastening portion is adjusted relative to the first fastening portion to facilitate fastening engagement therebetween upon folding the absorbent garment longitudinally.