Apparatus for forming in a sheet a fold extending transversely of the direction of sheet travel therethrough is provided with a triad of cylinders rotating about parallel axes. The sheets to be folded are first engaged about the periphery of a first of said triad of cylinders with their trailing and leading edges engaged by releasable grippers. A folding blade located between said grippers on said first cylinder causes a portion of the sheet intermediate the leading and trailing end thereof to be engaged by a folding flap provided on a second of said triad of cylinders. The folding flap engages the sheet at an intermediate point thereon and draws the sheet off said first cylinder while the sheet ends are positively held in a controlled manner. The third of said triad of cylinders cooperates by engaging the leading end of said sheet as said sheet is drawn off said first cylinder by the second cylinder. Thus, the transverse fold is formed in the sheet while the trailing and leading ends of the sheet are supported to avoid the occurrence of distortions of the folded sheet.