Hydroxyapatite (HAP) has tremendous applications in orthopaedics and dentistry fields due to its enhanced biocompatibility and bioactivity. In the present investigation, ethanol-based HAP nanoparticles (NPs) are prepared by sol–gel method using calcium nitrate tetrahydrate and triethyl phosphite, without using any additives or chelating agents. The sol–gel-derived HAP NPs were characterised using FT-IR, XRD, TGA-DTA, SEM-EDAX, ICP-OES and TEM analyses. In vitro cytocompatibility assessment of different concentrations of HAP NPs (200–1000 μg/ml) was performed using cultured NIH-3T3 fibroblast cell for 24–48 h. The results indicated that HAP NPs did not have any cytotoxic effects on NIH-3T3 cells. Further to this study, sol–gel-derived HAP sol was coated as triple layers on the Ti-6Al-4V by spin coating technique and the developed coatings were characterised by SEM-EDAX to determine the surface uniformity, chemical composition and thickness. The surface wettability of the coatings was observed by contact angle measurements. In vitro corrosion test was carried out in SBF solution and confirms that triple layer HAP coatings derived at 3000 RPM and sintered at 500 °C for 2 h exhibit higher corrosion resistance behaviour. This in vitro corrosion study predicts the suitability of the coatings for its long-term applications in medical field. In vitro cytocompatible study proves that HAP coatings on Ti-6Al-4V play a significant role in the enhancement of cell viability with prominent cellular response. © 2017 Informa UK Limited, trading as Taylor & Francis Group.