Using a completely randomized design experiment, the effect of different levels of diesel and spent engine oil contamination (0 mL/kg, 25 mL/kg, 50 mL/kg and 75 mL/kg of soil) on growth performance (seedling height, collar diameter, number of leaves and biomass accumulation) of Hildergardia barteri seedlings were assessed for twelve weeks. The concentration of Lead, Nickel, Copper and Zinc in the plant parts were also determined. Data were analysed using descriptive and inferential statistics at P<0.05 level of significance. There were significant differences in the effects of diesel and spent engine oil on growth performance of seedlings based on contamination levels. Control treatment had the highest height (92.43±5.13 cm), collar diameter (16.23±0.98 mm), number of leaves (11.21±0.47) and total biomass (33.01±12.79 g). Seedlings exposed to 50 mL/kg treatments had the least height (diesel oil: 78.21±7.22 cm; spent engine oil: 79±6.24 cm); those exposed to 75 mL/kg contamination had the least collar diameter (diesel oil: 8.85±1.05 mm, spent engine oil: 12.02±1.01 mm), while seedlings treated with 50 mL/kg diesel oil (2.21±0.37) and 75 mL/kg spent engine oil (4.79±0.55) had the lowest number of leaves. Heavy metal bio-accumulation ranges were: Lead: 0.17-0.39 mg/kg, Nickel: 0.09–0.45 mg/kg, Copper: 0.54–1.08 mg/kg, Zinc: 0.88–1.58 mg/kg. The ability of the seedlings to survive and bio-accumulate heavy metals indicate the potential phytoremediation capabilities of Hildergardia barteri. Keywords: phytoextraction, hydrocarbon derivatives, growth inhibition, Hildergardia barteri