Rhodiola rosea produces nearly 150 bioactive compounds. Cinnamyl alcohol glycosides (CAGs) are among the most important secondary metabolites which are specific to this plant species, exhibiting adaptogenic properties along with salidroside. However, raw material supplies for the pharmaceutical industry are hindered by limited access to the plant material. The species is endangered and protected in many areas: cultivation is long and ineffective. Precursor feeding has been found to be an effective strategy for improving the production of secondary metabolites in various plant tissues cultures, including in Rhodiola species. In this study, whole R. rosea plants grown in vitro were subjected to three different precursor treatments, including with trans-cinnamic acid, cinnamaldehyde and cinnamyl alcohol at 2 mM concentrations. The different treatments affected the secondary metabolite production differently. Trans-cinnamic acid did not affect the synthesis significantly, which contradicts earlier studies with cell suspensions. On the other hand, cinnamyl alcohol and cinnamaldehyde were beneficial, improving the production rate of rosin and rosavin by 13.8- and 6.9-fold, and 92.7- and 8.0-fold, respectively. The significant improvement in CAG accumulation due to cinnamaldehyde treatment was unexpected based on previous studies. In addition, cinnamaldehyde triggered the production of rosarin, which the other two treatments failed to do. The study presents the beneficial application of precursors to whole plants grown in vitro.