Bacterial growth on implant surfaces poses a significant problem to the long term success of dental and orthopedic implants. There is a need for implant surfaces which promote osseointegration, while at the same time decreasing or preventing bacterial growth. In this study, we adapted existing methods for measurement of bacterial biofilms, to be suitable for measuring the bacterial growth on implant surfaces. We used two different strains of bacteria, Pseudomonas aeruginosa and Staphylococcus epidermidis, and investigated the in vitro effect of bacterial growth on titanium surfaces coated with an ultrathin (20–40 nm thick) layer of nanosized hydroxyapatite (HA). We found that after 2 hours of biofilm growth, there was a 33% reduction of bacteria for both S. epidermidis and P. aeruginosa on nanosized HA compared to Ti. For a more mature 24 h biofilm, there was a 46% reduction for S. epidermidis and a 43% reduction for P. aeruginosa on nanosized HA compared to Ti. This shows that nanosized HA can be of benefit in reducing implant related infections, together with antimicrobial therapy.