This study was carried out to determine effects of plant density and number of eyes per seed pieces on yield and tuber size of potato (Solanum tuberosum L. cv Agria) in Turkey during 2011 and 2012 crop seasons. Treatments were arranged as a split plot design with plant density (distance on rows 20, 25 and 30 cm) as main plots, eyes number (2, 4 and 6 eyes) per seed piece as sub plots. Total tuber yield, yield of Grade C (45-35 mm) and Grade D (35-25 mm) sized tubers significantly increased with the increasing planting density. Number of tubers per plant, average tuber weight, tuber yield per plant and yield of Grade A (>60 mm) sized tubers significantly decreased with the increasing of plant density. With the increasing number of eyes in seed pieces, while tuber number per plant and yield of Grade C and Grade D sized tubers increased, average tuber weight decreased. The highest total tuber yield (40.6 t/ha) and Grade B (13.0 t/ha) and Grade C (15.3 t/ha) were obtained in the distance of rows at 20 cm and four eyes cut seed tubers. In conclusion, with the increase of the planting density and eyes number in seed piece, we noticed some decline in marketability and an increase the yield of seed tubers.