A mixture of four isolates of Fusarium oxysporum, the causal agent of cotton damping-off, five biocontrol agents (Bacillus subtilis, Pseudomonas fluorescens, Streptomyces griseus, Trichoderma harzianum and Trichoderma viride), and fungicide Monceren were evaluated on cotton cultivar Giza 90 (Gossypium barbadense L.) in the presence and absence of humic acid (potassium humates) which was applied as soil drench. The disease incidence was evaluated as seedling survival, plant height, and dry weight. Activities of some oxidative enzymes (peroxidase, polyphenoloxidase and catalase) were also evaluated. The results showed that humic acid caused deleterious effects on seedling stand, plant height and dry weight of cotton cultivar Giza 90. The application of some biocontrol agents negated these deleterious effects. Therefore, from practical stand point, it is not desirable to use humic acid if the soil is infested with Fusarium oxysporum. If it is necessary to use humic acid; this should be accompanied by the application of suitable biocontrol agent