The aim of this experiment was to evaluate by-products of olive oil production in compost production and to test them in different rates as tomato ('Melis') seedling growing medium. Therefore, three different types of olive oil production wastes (two-phase and three phase olive mill wastes and olive oil waste water sludge) were composted with separated dairy manure, poultry manure, and straw using aerated static pile composting methods to obtain three different types of composts separately. Additionally, each compost was enriched with cotton seed meal, potassium salt, and rock phosphate. In the experiments, different rates (25, 50, 75 and 100%) of six different composts were added to peat which is locally available. Seeds were sown on July 21, 2015. Each treatment had 4 replicates and each replicate included 64 plants in a tray. Seedlings were fertilized by liquid composted farmyard manure and seedlings were ready for transplanting after a month. Some physical and chemical properties of each growing medium, germination rate of seeds and seedling vigor were determined. Germination period extended with the increase of compost rates in peat. Compost materials obtained from the mixture of olive oil production wastes were found to be appropriate in composting without a need of enrichment and their performances were close each other due to the changes in terms of their effects on tested characteristics. However, results were promising in order to be able to evaluate the olive oil wastes in seedling production and a rate of 25% could be proposed.