Phage therapy, the use of viruses that infect bacteria (bacteriophages), is being trialled as a complement to antibiotics during the antimicrobial resistance crisis. While bacteria can evolve bacteriophage resistance, bacteriophages can evolve to increase their infectivity against resistant bacteria (coevolution). Additionally, bacteriophage resistance is hypothesised to be beneficial in phage therapy by increasing bacterial susceptibility to the immune system. Trade-offs between immune and bacteriophage susceptibility may affect bacteria-bacteriophage coevolution by increasing the costs of acquiring more resistance mutations and reducing mutation rates. Here, we examine how a pathogenic bacterium, Pseudomonas aeruginosa coevolves with two clinically relevant bacteriophages (14-1 and PNM) when in the presence of macrophages (RAW 264.7 cell line). Bacteria were shown to have increased survival in the short-term when macrophages were present, leading to increased rates of bacteriophage resistance over one week. Macrophages inhibited bacteriophage infectivity evolution without phagocytosing bacteriophages. We hypothesise that the spatial structuring introduced by macrophages may reduce bacteria-bacteriophage population mixing, slowing rates of coevolution and leading to increased bacterial resistance. These results have implications for our understanding of the immune-system’s role in influencing phage therapy outcomes.