Oil palm (Elaeis guineensis Jacq.) plays an important role in Benin’s economy. The present study aimed to evaluate the effect of two substrates and their treatments on oil palm seedlings in pre-nursery. An experiment was conducted to evaluate the effect of undergrowth potting soil and slush and their treatment with the fungicide Topsin M on the agronomic performance of the seedlings in pre-nursery. The experimental design used was a complete random block with four treatments after combining the two factors (substrate and fungal treatment). These were: untreated understory potting soil, treated understory potting soil, untreated slush and treated slush. The number of plants emerged, the number of dead plants, the number of leaves and the height of the plants were the parameters measured on the juveniles of the oil palm. The results of the study showed that the substrate of understory potting soil treated with Topsin M significantly (p˂0.05) promoted the emergence of 100% of seedlings and vegetative growth (i.e. 3 leaves and 17.66 cm in height). In conclusion, the use of understory potting soil substrate treated with Topsin M for the production of oil palm seedlings could therefore improve their quality and reduce the burden on producers in the search for the right planting material.