<p><i>Cyathea delgadii</i> Sternb. is a tree fern species belonging to the family Cyatheaceae, distributed from Central America across the Andes and the Guyanas to eastern Brazil and the central Brazilian highlands. The aim of the study was to investigate the effect of thidiazuron (TDZ; 1-phenyl-N-(1,2,3-thiadiazol-5-yl)urea) on the proliferation of shoot apical meristem tissue of <i>C. delgadii</i> derived from axenic sporophyte cultures grown on hormone-free ½MS medium. Explant cultures were maintained in two stages: the first stage involved culturing the shoot apical meristems on media supplemented with various concentrations of TDZ (5.0, 1.0, 0.1, and 0.01 µM) and 0.25 µM NAA for four months, after which explant response and the number of regenerants were assessed. In the second stage, cultures were transferred to hormone-free ½MS medium for an additional six months, which promoted leaf and root formation and resulted in mass regeneration of sporophytes. Over the 10-month culture period, four parameters were analyzed: (1) number and (2) length of regenerated leaves, and (3) number and (4) length of regenerated roots per sporophyte. Out of 200 initial explants, 71 produced overgrown meristematic tissue that developed into green globular bodies (GGBs) and subsequently numerous sporophytes. The primary explant response during long-term culture depended on the TDZ concentration used. Ultimately, 1,490 regenerants (sporophytes) were obtained. Pearson’s correlation analysis revealed a strong positive association (<i>r</i> = 0.641) between root length and leaf length at 1.0 µM TDZ, whereas the lowest correlation (<i>r</i> = 0.003) was observed between root number and leaf length.</p>