The influence of various concentrations of the standard fertilizer on the performance of seedling grafts tomato was investigated using coconut coir containing root media. Two different formulations of coir dust (CO) with perlite (PL) and vermiculite (VM) (5:5 and 7:3 mixtures of CO+VM and CO+PL, v/v) were used as growing media. Five variations (0, 0.1, 1, 2, 4x conc.) of a standard fertilizer (SF) containing ($mg{cdot}L^{-1}$) 190 N, 54.5 $P_2O_5$, 149 $K_2O$, 542 CaO, 24.3 MgO, 19.5 S, and micronutrients in pre-plant fertilizers were used for seedling growth before grafting. The root stock (cultivar J3B Strong) and scion (cultivar Sunmyung) were grown in 50 cell (volume 33 cc) and 105 cell (volume 18 cc) trays, respectively. Both were fertilized once a week with the N concentrations of 50, 120, and $200mg{cdot}L^{-1}$ (using 14-00-14 and 20-10-20 commercial analysis fertilizers alternately) in stages 2, 3, and 4, respectively. At 31 days after sowing, seedling plants of both the root stock and scion were excised above the soil line, trimmed, and used for seedling grafting. The cut grafted plants were planted into the 50-cell pack trays (cell volume 33 cc) and incubated for 7 days inside a plastic tunnel under a shade cloth for callusing and adventitious root formation. After an additional 7 days of gradual acclimatization with lower humidity, the rooted grafted plants began to receive fertilizer treatments once a week. When examined 31 days after sowing, the highest weights of the root stock seedlings were obtained with the 2x SF solution in CO+PL mix (4.1 g/seedling) and 1x SF solution in CO+VM mix (5.0 g/seedling). The electrical conductance (EC) of the soil extracts for the two treatments were 3.85 and $1.94dS{cdot}m^{-1}$, respectively. Fresh weights of the grafted plants (Sunmyung/J3B Strong) grown in CO+VM and CO+PL mixes were not significantly different from each other when measured 13 days after grafting. Elevated plug-phase fertilizer levels in CO+PL mix resulted in an increase of fresh weights from the grafted plants in 13 days. However, substrate EC ($5.19dS{cdot}m^{-1}$) at 4x SF solution in CO+PL mix was much higher than that recommended for plug seedling production. Grafted plants were tolerant to high salinity. Fresh weights of grafted plants were higher when grown with $200mg{cdot}L^{-1}N$ in CO+PL mix or $100mg{cdot}L^{-1}N$ CO+VM mix than other treatments. The substrate ECs of the two treatments were 3.85 and 1.94 $dS{cdot}m^{-1}$, respectively. Grafted plants grew well when exposed to elevated substrate salt concentrations. Results of this experiment suggest that the production of high quality tomato seedling grafts is possible with salt concentrations much higher than that recommended for plug seedling production. The optimum fertilizer concentration, however, must be determined separately for a given root medium mixture containing coconut coir.