Depending on the coating method utilized and subsequent heat treatments (such as through the use of plasma-spray deposition), inter-diffusion of atomic species across titanium (Ti) and hydroxyapatite (HA) coatings may result. These events may lead to structural and compositional changes that consequently cause unexpected HA phase transformations which may clearly influence the performance of an orthopedic implant. Thus, the objective of the present in vitro study was to compare the cytocompatibility properties of chemistries that may form at the Ti:HA interface, specifically HA, tricalcium phosphate (TCP), Ti doped HA, and those containing calcium titanate (CaTiO3). In doing so, results of this in vitro study showed that osteoblast adhesion increased with greater CaTiO3 substitutions in either HA or TCP. Specifically, osteoblast adhesion on HA and TCP composites with CaTiO3 was almost 4.5 times higher than over pure HA. Material characterization studies revealed that enhanced osteoblast adhesion on these compacts may be due to increasing shrinkage in the unit lattice parameters and consequent decrease in grain size. Although all CaTiO3 composites exhibited excellent osteoblast adhesion results, Ca9HPO4(PO4)5OH phase formation into TCP/CaTiO3 increased osteoblast adhesion the most; due to these reasons, these materials should be further studied for orthopedic applications.