Monitoring system for a conveyor of articles (100). The conveyor of articles comprises at least one transport chain (105) adapted to be moved along a movement direction, and a guide structure (132) of the transport chain comprising a lower guide element (135) adapted to support the chain from below and a higher guide element (140) adapted to insist on the chain from above and facing toward the lower guide element. The system comprises at least one first magnetic field generator element (155) located in a first guide element, at least one magnetic field sensor (160) located in a second selected guide element for sensing the magnitude of a measure magnetic field, and processing means (165) for quantifying a reduction of the overall thickness of the chain based on a time variation of the measure magnetic field.