Aim of this study was to investigate the effects of feeding tanniniferous oak (Quercus hartwissiana) leaves with or without a tannin binding agent, polyethylene glycol (PEG), on rumen protozoa in Tuj lambs. A total of 42 lambs (8-9-month-old) were equally divided into 7 groups as follows: 1) control (0 g leaf + 0 g PEG); 2) 185 g leaf + 0 g PEG; 3) 185 g leaf + 10 g PEG; 4) 185 g leaf + 20 g PEG; 5) 370 g leaf + 0 g PEG; 6) 370 g leaf + 20 g PEG; 7) 370 g leaf + 40 g PEG. All groups were given 272 g concentrate and varying amounts of hay, such that the amount of leaf plus hay was equal to 645 g. The experiment continued for 60 days following adaptation period and the lambs were kept in individual cages. Rumen samples were taken 2 h post-feeding in the middle (Day 30) and at the end of the experiment (Day 60). It were determined the ciliate protozoa counts and the differential protozoa counts in the rumen contents. Total protozoa counts of groups were 799x103/ml, 924 x103/ml, 1014 x103/ml, 729 x103/ml, 824 x103/ml, 717 x103/ml and 872 x103/ml, respectively for groups 1-7 in the middle of the experiment (Day 30) and were 678 x103/ml, 755 x103/ml, 972 x103/ml, 637 xlCP/ml, 693 x103/ml, 765 x103/ml and 1026 x103/ml, respectively for groups 1-7, at the end of experiment (Day 60), respectively. In the study, eight species of protozoa were identified belonging Holotrich (Isotricha intestinalis, Isotricha prostoma and Dasytricha ruminantium) and Oligotrich families (Entodinium minimum, Entodinium caudatum, Diplodinium spp, Epidinium ecaudatum and Ophyroscolex caudatum). Entodinium spp. were dominant (approximately 90 %). There were no significant differences (P>0.05) in the protozoa counts and the differential protozoa counts between groups and sampling times (Days 30 and 60). In conclusion, there was no effect the level of oak (Quercus hartwissiana) leaf intakes in the study and PEG supplementation to the diet on rumen protozoa in Tuj lambs.