Phenolics and secoiridoids from crude olive mill wastewater (OMW) were purified using a preparative hybrid separation process: pressure-driven cross-flow membrane micro-(MF) and ultrafiltration (UF) and solid phase extraction (SPE). Five fractions with different contents of these compounds were obtained and their antibacterial activity against several strains of Campylobacter was evaluated. The results showed that the fraction with the highest content of phenolic and secoiridoid compounds had a relevant antibacterial activity against all tested strains with a strain-dependent character. Pre-treatment of LPS-stimulated cells with this fraction decreased the production of nitric oxide (NO), showing its potential as anti-inflammatory agent. Finally, the effect of the same fraction on the viability of human intestinal epithelial cell lines was evaluated. In conclusion, OMW could be useful as a potential source of bioactive compounds against Campylobacter, increasing the valorisation of olive oil by-products.