In this study, cinnamaldehyde (CAD) was used as a filler modifier and antimicrobial material for silica‐filled styrene butadiene rubber (SBR) composite. CAD was used in different amounts to modify the silica surface. Fourier‐transform infrared spectroscopy (FTIR) was used to characterize the obtained CAD modified silicas. The modified silicas were mixed with SBR matrices using a laboratory two‐roll mill to produce modified silica‐filled SBR composites. The curing, mechanical, swelling and antibacterial properties of the resulting composites were studied and compared with those of the unmodified silica‐filled SBR composite. The surface morphologies of the obtained composites were also studied. The mechanical results showed that the use of 3 g of CAD resulted in a significant improvement in the mechanical properties of the resulting composite as its tensile strength, elongation at break and modulus at 100% increased by 144.9%, 105.1%, and 37.5%; respectively; compared to the unmodified composite. Furthermore, the antibacterial results showed that all the modified composites had a high activity against Gram+ and Gram− bacteria compared to the unmodified one, and this activity increased by increasing the amount of CAD. Accordingly, it is expected that these prepared composites can be used for medicinal purposes in the future.