Increasing bacterial resistance and a corresponding decrease in antibiotic discovery has made the development of new antibiotic therapies a high priority. Combinational approaches may be effective in overcoming resistance and potentiating the activity of conventional antibiotics that are otherwise ineffective against resistant bacteria. Moringa oleifera leaf, fruit pulp and seeds were extracted and investigated for the ability to inhibit bacterial growth using disc diffusion and liquid dilution MIC techniques. The extracts were also combined with conventional antibiotics and tested against the microbial triggers of some autoimmune diseases. Whilst some M. oleifera extracts were effective bacterial growth inhibitors, the majority had only low to moderate activity. The seed ethyl acetate and chloroform extracts were particularly noteworthy against Klebsiella pneumoniae (MICs of 976 and 402 μg/mL respectively) and against Proteus vulgaris (MICs of 500 and 938 μg/mL respectively). However, combinations of the M. oleifera extracts with conventional antibiotics proved substantially more effective. In total, 27 combinations were synergistic (18 against P. vulgaris, 1 against K. pneumoniae, 5 against Acinetobacter baylyi and 3 against Pseudomonas aeruginosa). Notably, several antibiotics with low inhibitory activity alone were returned to a state of substantial activity when tested in combination with the extracts. Moringa oleifera extracts may function as resistance modifying agents, potentiating the activity of several antibiotics that are relatively ineffective alone. Identification of these agents may be highly beneficial in drug design against several bacteria.