Petroleum companies all over the world are facing numerous issues related to microbially influenced corrosion (MIC), despite the routine application of biocides and corrosion inhibitors. This sector is in dire need of innovative products with multifunctional properties. The idea of combining the properties of two chemical products has captured the attention of researchers. Therefore, this study aimed to synthesize a hyperbranched poly(amidoamine) dendrimer (PAMAMD) and its ZnO nanohybrid (PAMAMD-Zn). The synthesized products were characterized using various techniques; FT-IR, XRD, DLS, and SEM. Subsequently, the synthesized products were tested for their broad-spectrum antimicrobial activity. Additionally, they were evaluated for their suitability as biocides and corrosion inhibitors against aerobic and anaerobic corrosive bacteria isolated from an Egyptian petroleum company's environment. The results were notably intriguing, as both the synthesized products, PAMAMD and PAMAMD-Zn, demonstrated broad-spectrum antimicrobial activity against various standard microbial strains. Notably, PAMAMD-Zn exhibited higher broad-spectrum antimicrobial activity with the lowest MIC/MBC and MFC values compared to PAMAMD. Furthermore, both products have exhibited biocidal and corrosion inhibition efficiencies against aerobic and anaerobic corrosive communities. PAMAMD has displayed the highest metal corrosion inhibition efficiency of 92.1% while PAMAMD-Zn, was with an efficiency of 94.4% against the aerobic corrosive bacterial community. Similarly, the synthesized inhibitor PAMAMD has shown a corrosion inhibition efficiency of 91.6%, slightly lower than that detected for the inhibitor PAMAM-Zn, which exhibited an efficiency of 96.3% against the anaerobic corrosive bacterial community. In conclusion, two synthesized products with multifunctional properties, including broad-spectrum antimicrobial activity, biocidal effects, and corrosion inhibition, have been successfully developed in this study.