The date palm has economic importance in the world, especially in the Middle East. In this investigation, the effect of three different Chaetomium species on infected date palm plants with different fungal pathogens i.e., Rhizoctonia solani, Fusarium oxysporum, F. chlamydosporum, and F. solani was studied. Pathogenicity tests of root rot pathogens on date palm seedlings were carried out, F. oxysporum was the most virulent isolate which gave the highest percentage of diseases incidence after 45 days (55.5%) while the least virulent isolate was F. solani 1 and F. verticillioides which gave (11.7 %). Nine isolates of Chaetomium spp. suppressed the radial growth of root rot pathogens. The mode of action of Chaetomium isolates towards pathogens varied, some isolates suppressed the growth of the pathogens while others showed moderate inhibition of the mycelial growth of pathogens. C. globosum isolate No. 2 was chosen depending on the antagonism test that gave a highly significant growth reduction of the pathogen. C. globosum isolate No. 2 was the best isolate in controlling root rot disease incidence. Biochemical changes in the treated plants, phenol, indol acetic acid and polyphenol oxidase enzyme (PPO) activity were decreased in infected plants with the tested fungal pathogens, however, were increased in plants treated with C. globosum and in plants treated with a mixture of fungi and C. globosum compared with control and fungicide treatments. Chlorophyll a and b were increased in plants treated with a mixture of the tested fungi and C. globosum compared with all, while carotenoids were increased in infected plants with F. solani, R. solani, and F. oxysporum, respectively compared with other treatments. CAT enzyme activity was increased in infected plants with any of F. solani, F. oxysporum and R. solani.