Studying about the effect of four pseudomonas and two Serratia isolates on growth of Fusarium oxysporum showed that, Pseudomonas fluorescens No.2 & No.3 and Serratia marcescens No.2 gave highest inhibition zones which were 37.33, 35,00 and 31.33 mm, respectively. Evaluating about the effect of Pseudomonas and Serratia culture filtrates at three concentrations (10, 25, 50%) on the linear growth and spore germination of Fusarium oxysporum revealed that, all filtrates of the tested isolates reduced the mycelial growth and spore germination of F. oxysporum. All filtrates of the tested isolates at 50% concentration completely inhabited spore germination of F. oxysporum. Culture filtrates of Pseudomonas putida and Serratia marcensensNo.2 at 50% concentration reduced the mycelial growth of F. oxysporumby 80.74 and 80.37% respectively. In this respect, all tested isolates made lysis to mycelial of F. oxysporum except Pseudomonas fluorescensNo.3. Effect of treating cucumber seeds with cell suspension of Pseudomonas and Serratia isolates on incidence of Fusarium wilt disease revealed that all isolates were effective in reducing disease incidence and disease severity and increasing the percentage of healthy plants compared to the control. Pseudomonas fluorescens No.3 and Serratia marcensens No.2 were the best isolates and completely prevented the disease incidence. Key words: Cucumber, fusarium wilt, pseudomonas, serratia and greenhouses.