The Kenaf and rosella plants can grow in various types of land, and the fibers have been used as a reinforcement material for polymer composites, the automotive industry, rope, and paper. Some factors influenced the fiber properties, including the plant species, the growth site type, the plant’s axial position, and harvesting time. Still, variety in the fiber properties before the harvesting period and axial position of plants have not been reported before. Thus, this study investigated the effect of the harvesting period and axial position of kenaf and roselle (top, middle, and bottom) on fiber dimension properties and their derived value. The harvesting period tends to increase the all-fiber dimension properties of kenaf. However, this tendency only occurs in the cell wall thickness, and fiber length of roselle fibers, while the fiber diameter and lumen cell before harvesting period are higher than during the harvesting period. The axial position of plants results in a variety of fiber dimensions. Except for the kenaf after harvesting, the fiber length of the kenaf and roselle stems increases from the base to the top of the stem in three axial positions. Based on fiber derivative values and fiber dimensions, roselle plants are more recommended as pulp and paper raw materials before harvesting time and during harvesting time than kenaf plants, with the proper stem position for pulp and paper raw materials being in the middle position of the stems before harvesting time.