Organic agricultural production and related food sector has become important in Turkey and over the world. Greenhouse production, especially with soilless culture techniques, might provide growers a viable system to become a consistent supplier of special crops year around for the organic market. Soilless organic systems could recover the disadvantages of soil based greenhouse production and it could create new opportunities for growers in the near future. An experiment was carried out to compare the effects of organic and syntheticinorganic fertilization on plant growth, nutrient status and yield of soilless grown summer squash. The cultivar 'Alata Yesili F-1' was grown in open perlite system during early spring in plastichouse. Two fertilization treatments; (1) control as conventional nutrition by synthetic fertilizers and (2) organic nutrition by plant extract and chicken manure, were used to grow the plants. Growth parameters, namely shoot fresh weight, leaf area, leaf number, root fresh weight and plant height were not different in both treatments for 30 days after transplanting. However, 60 days after transplanting synthetic fertilized plants had 18%, 12%, 25% and 27% higher shoot fresh weight, leaf area, root fresh weight and plant height, respectively. Organic fertilized squash plants had 25% less yield in comparison to synthetic fertilized plants. Number of fruit was less affected from the treatments. However difference in mean fruit weight was 19% and organic fruits were smaller. Therefore the organic fertilized plants had similar number of fruit, but the size of fruits was smaller. Concentrations of N, P, K, Ca, Mg, Fe, Mn, Zn and Cu in plant samples were similar or had some small differences between two nutrition treatments.