In the present study, biodegradable poly(amidoamine) dendrimers (PAMAM G1/G2/G3) was covalently functionalized with carbon nanotubes (CNTs) and nanostructured hydroxyapatite was immobilized onto CNTs-PAMAM matrix through coordination bond between the -NH2 groups of dendrimer and Ca2+ of hydroxyapatite. The structural and morphological behaviors of the nanohybrids were established through spectroscopic and microscopic analyses. In vitro cytotoxicity and cell proliferation was assessed through osteoblast-like MG 63 cell line using 3-4, 5-dimethylthiazole-2-yl, 2,5-diphenyl tetrazolium bromide assay for 3days. The more abundant of -NH2 group exist in PAMAM(G3) dendrimer attracts more number of HAp molecules onto their surface which exhibits enhanced activity in cell proliferations even at higher concentrations.