Mechanical conditioning of seedlings is a process that creates specific stresses in plants, to which they respond by decreasing growth in height and developing thicker and stronger stems. The aim of this study was to determine the effect of brushing (0, 10 and 20 strokes per day) and plant density (40 and 84 pots per tray) on the growth of coriander and thyme seedlings during the winter period. The seedlings were treated with a jute cloth in the period from the appearance of the cotyledon leaves until the stage of transplantation. Brushing of coriander seedlings reduced the seedling height and the fresh mass of leaves and roots only at the higher plant density (84 pots per container), with a greater effect of 10 strokes per day. Also, leaf dimensions were reduced, both by 10 and 20 strokes per day and independently of the plant density. Dry matter content in leaves and root was increased by 10 strokes per day, but no effect on the number of leaves per seedling was recorded. At thyme seedlings cultivated in a higher plant density (84 pots per container), brushing significantly reduced the height of the seedlings, the leaf size, the fresh mass and the dry matter content of the aboveground plant part, and the greater effect was achieved with 20 strokes per day. No influence on number of nodes and shoots per plant was observed. Cultivation of seedlings in multi cell trays with 84 pots can be recommended for both plant species, along with brushing with 10 strokes per day for coriander and with 20 strokes per day for thyme.