Arnica or mountain arnica (Arnica montana L.) is a herbaceous perennial, medicinal plant species. It is authentic in mountainous areas of the western part of Croatia and in some European countries. Due to the high demand for flowers, herb and roots in local and international market, there is a need for the introduction of this strictly protected plant in agricultural production. Obstacle to more intensive introduction of arnica on agricultural area presents the lack of large-scale cultivation of transplants, due to the slow initial growth of the plants. It is assumed that plant growth stimulators can accelerate the production of arnica transplants. The aim of this research was to study the influence of selected biostimulators on dynamics of pricked and unpricked transplants of arnica. The experiment included one fertilization treatment (Osmocote) and two treatments with plant growth stimulators (Bioplantella Super-F and Eko-Rast Vrtko), while part of the plants was not treated and represented control. Sowing was performed on March 11, 2015, in polyethylene containers with 67 pots, 9 cm deep. On April 15, 2015, began foliar treatments with plants growth stimulator and 6 treatments were performed. After the half of all number of treatments with biostimulators, on May 21, 2015, pricking of arnica transplants was carried out. Morphometric analyses were conducted on May 21 on unpricked transplants and on July 6, on pricked transplants. Relative growth of arnica transplants was monitored on its biomass (length × width of the largest leaf × number of leaves per plant). It was found that the application of Osmocote fertilizer with foliar application of biostimulants Eko-rast Vrtko resulted in a significant increase of pricked transplants. The application of biostimulant Bio Plantella Super-F was not justified and is not recommended in the production of arnica transplants.