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The role of <i>Pythium oligandrum</i> as a biocontrol agent against <i>Pythium aphanidermatum</i> was investigated to avoid the harmful impacts of fungicides. Three isolates of <i>P. oligandrum</i> (MS15, MS19, and MS31) were assessed facing the plant pathogenic <i>P. aphanidermatum</i> the causal agent of <i>Glycine max</i> damping-off. The tested <i>Pythium</i> species were recognized according to their cultural and microscopic characterizations. The identification was confirmed through sequencing of rDNA-ITS regions including the 5.8 S rDNA. The biocontrol agent, <i>P. oligandrum</i>, isolates decreased the mycelial growth of the pathogenic <i>P. aphanidermatum</i> with 71.3%, 67.1%, and 68.7% through mycoparasitism on CMA plates. While the half-strength millipore sterilized filtrates of <i>P. oligandrum</i> isolates degrade the pathogenic mycelial linear growth by 34.1%, 32.5%, and 31.7%, and reduce the mycelial dry weight of the pathogenic <i>P. aphanidermatum</i> by 40.1%, 37.4%, and 36.8%, respectively. Scanning electron microscopy (SEM) of the most effective antagonistic <i>P. oligandrum</i> isolate (MS15) interaction showed coiling, haustorial parts of <i>P. oligandrum</i> to <i>P. aphanidermatum</i> hyphae. Furthermore, <i>P. oligandrum</i> isolates were proven to enhance the germination of <i>Glycine max</i> seedling to 93.3% in damping-off infection using agar pots and promote germination of up to 80% during soil pot assay. On the other hand, <i>P. oligandrum</i> isolates increase the shoot, root lengths, and the number of lateral roots.