The increasing discharge of Spent Engine Oil (SEO) into the environment poses severe ecological risks due to its toxic and recalcitrant components. This study explored SEO-tolerant actinobacteria for nanobioremediation of SEO. Actinobacteria were isolated from metal dumpsite soil and screened for tolerance to SEO. Identified strains were used to synthesise iron-based nanoparticles and characterised using UV, SEM, FT-IR and XRD. The remediation potential of the synthesised nanoparticle was assayed in a pot experiment involving SEO-contaminated soil (SCS) + 1% nanoparticle (treatment) and SCS + sterile water (control). Degradation rate was confirmed using phytotoxicity and gravitational assay. Morphological characteristics of isolates are chalky-white to grey, filamentous aerial hyphae, powdery spore surfaces, and Gram-positive reactions, suggesting their actinobacterial traits. Molecular identification using 16S rDNA sequencing confirmed the most effective isolate as Streptomyces, showing close phylogenetic relationships to known hydrocarbon-degrading strains. Synthesised nanoparticle was confirmed by UV-Vis absorption at 420 nm. SEM revealed an agglomerated spherical nanoparticle with tightly packed masses that tend to flocculate. FT-IR detected hydroxyl, amide and carbonyl groups responsible for enhancing the conversion and stability of nanoparticles. XRD confirms the formation of well-crystalline nanoparticles. Phytotoxicity study showed that nanoparticle-treated soil (16.3 cm, 2.0 cm, 0.508 g) has significantly higher shoot height, root length and dry root weight of Phaseolus vulgaris than the control (5.3 cm, 0.6 cm, 0.108 g), respectively. Gravitational assay revealed SEO degradation efficiencies of 72%. The findings demonstrate that SEO-tolerant Streptomyces can biosynthesise stable nanoparticles that accelerate SEO degradation and reduce toxicity.