Seedling diseases of maize are caused by a complex of organisms, including fungi in the genus Fusarium. Root-lesion nematodes (Pratylenchus spp.) are common in fields where maize is grown, and they are known to interact with Fusarium spp. in several crops. The objectives of this study were to assess the impacts of seed treatment combinations on maize seedlings coinfected with Pratylenchus penetrans and two Fusarium spp. that cause seedling disease symptoms (Fusarium graminearum and F. verticillioides) and to determine whether there were interactions between P. penetrans and the Fusarium spp. Growth-chamber experiments were conducted with fungicide- or nematicide-treated or untreated maize seed planted in a sand-soil mixture infested with inoculum of either F. graminearum or F. verticillioides. A suspension of 4,000 P. penetrans (mixed stages) was added to the pots at the time of planting. After 30 days, shoot length and fresh and dry shoot and root weights were determined. Total root length and fine root length, root volume, numbers of root tips and forks, and root surface area were measured through analysis of digital images of the root systems. After 42 days, P. penetrans nematodes were extracted and quantified from roots and soil. There were significant effects of the treatments on root health with interactions between Fusarium spp. and P. penetrans. F. graminearum caused the greatest reductions in root and shoot growth, and interactions with P. penetrans were more evident for F. verticillioides than for F. graminearum. Image analysis of root system architecture showed that seed treatment significantly improved root system characteristics. Seed treatments containing the nematicide abamectin in combination with fungicides reduced root infection by P. penetrans and provided the healthiest root system when under attack by the Fusarium–Pratylenchus complex.