A greenhouse experiment aimed at investigating the effect of four chelates, differing in percentage of Fe content and the kind of Fe bonding ligand: Fe 8 Forte (EDTA+HEEDTA), Fe 9 Premium (DTPA), Fe 13 Top (EDTA) and Librel Fe DP7 (DTPA), on the state of iron nutrition of Merkury F1 cultivar greenhouse tomato grown traditionally in peat substrate. The second factor was iron content in the growing medium, which was established to reach the following levels: 50, 75 and 100 mg Fe dm-3, while in the control object Fe values ranged 17.9 Fe dm-3 (after peat liming). The experiment was established in a two-factorial design with three replications including four plants cultivated on one plot. The iron content was assayed in plant index parts according to the ASA method. On the basis of the results, significant differences were found in the state of greenhouse tomato nutrition under the influence of the examined iron chelates. The highest content of iron in tomato leaves was determined when chelate Fe 9 Premium (DTPA) was used, which points to the fact that it was the best source of Fe. The lowest iron level was recorded after the application of Fe 13 Top (EDTA). The highest mean Fe content for the years and dates of analyses appeared in leaves of plants cultivated in the growing medium containing 75 mg Fe dm-3. In June, after the plants began to yield, there was a considerable decrease in the Fe content in plant index parts in comparison to the stage of fruit maturation and the end of yielding. The study did not demonstrate any symptoms of phytotoxicity or visible disorders regarding tomato growth and development due to the examined Fe chelates introduced in the doses of 32.1, 57.1 and 82.1 mg Fe dm-3 to the substrate, whose initial Fe concentration after peat liming was on average 17.9 mg Fe dm-3.