Tomato (Solanum lycopersicum L.) is an agricultural crop that is produced in the warm part of the year outdoors or in sheltered areas throughout the year due to the extreme need for heat, but with the regulation of the temperature regime. For the most part, tomato production takes place by growing from seedlings in protected areas in specially prepared containers that differ in the number of sowing places or the volume of sowing places in which the root of the seedlings develops. The growth and development of tomato seedlings takes place during the spring season, when due to stress caused by external factors, seedlings may develop less, which is reflected in their quality. Biostimulators are used to overcome stress when growing seedlings. The aim of this study was to determine the influence of sowing site volume and biostimulators on the quality of tomato seedlings. For the purpose of the research, tomato seeds of the San Marzano variety were used, from which seedlings were grown in containers with 42 and 60 sowing sites with the use of biostimulators and without the use of biostimulators as a control. The quality of tomato seedlings was determined by measuring the following morphological properties: stem diameter, root length, stem length, number of leaves, aboveground part mass and root mass. Better quality was obtained in tomato seedlings grown in containers with a larger sowing volume and with the use of biostimulators.