In recent years, in addition to mineral fertilizers, biofertilizers containing the pure or mixture of different bacteria species that allow the uptake of nutrients have been used. Although widely used in agriculture, using of biofertilizers in forest nurseries is a relatively new application. There are limited researches about the effects of biofertilizers on morphological characteristics of forest tree seedlings, especially in outdoor environmental conditions of the nurseries. The current study was carried out to determine the effects of biofertilizers on the seedling morphological characteristics when applied on the seedbed of the forest nursery in outdoor conditions. In this research, 1+0 old Arizona cypress (Cupressus arizonica) and sugar maple (Acer saccharum) seedlings were used in Bursa Forest Nursery. Among the numerous commercial biofertilizers, two biofertilizers containing different bacterial compositions were chosen and applied in four different doses (3 ml/l, 15ml/l, 30 ml/l and control) for each to determine the effects on some morphological seedling characteristics. The applied biofertilizers and doses on the seedlings of C. arizonica and A. saccharum significantly affected some morphological characteristics, such as the seedlings’ heights and root collar diameters. In A. saccharum seedlings, 3 ml/l doses of both Best-doll and Bio-doll fertilizers increased the length of the seedlings by 13% and 11% and provided 13% and 16% better growth in the root collar diameters respectively, compared to the control. The C. arizonica control group seedlings produced higher diameters and height growths compared to two other biofertilized seedlings. The studies of biofertilizers should be continued on using of different doses, different forest tree species, soil conditions and the combined applications with chemical fertilizers.