Tantalum is one of the most corrosion-resistant materials and has mechanical properties that are suitable for orthopedic applications. However, tantalum exhibits bioinert characteristics and cannot promote the desired level of osseointegration with juxtaposed bone tissues. To enhance the bioactivity of tantalum, nanoscale surface modifications via anodization could be a potential approach. In this study, surface features having nanotubular, nanodimple, and nanocoral morphologies were fabricated onto tantalum by controlling anodization parameters. Aside from altering the surface morphology, nanotubular, nanodimple, and nanocoral feature sizes were precisely fine-tuned between the 20 and 140 nm range. The results indicated that anodized surfaces consisted of Ta2O5 and nonstoichiometric tantalum suboxide chemistry. Upon the anodization, surface area of the tantalum samples increased up to 2-fold, which was accompanied by up to a 3.5-folds increase in the nanophase surface roughness. Biological studies showed that anodized tantalum surfaces significantly enhanced protein adsorption and improved bone cell proliferation and spreading independently of the anodized surface morphology and feature size. Nanodimple surfaces having a 90 nm feature size promoted 50% more bone cell proliferation and 23% more cellular spreading compared to non-anodized tantalum. Nanodimple surfaces also enhanced alkaline phosphatase activity and increased Ca mineral deposition up to 5 weeks compared to non-anodized tantalum, indicating higher bioactivity. In this study, biological interactions of anodized tantalum surfaces having different morphologies and feature sizes were examined, for the first time, and the potential use of nanostructured tantalum was highlighted for orthopedic applications.