•Assessment of cellular response on 3-D printed macroporous PEEK scaffolds.•Macropores with uniform sizes and reproducibility were successfully fabricated.•Effects of the scaffolds’ macropores on osteoblast cellular functions were analyzed.•800 µm pore sizes provided greater surface area and enhanced cell-cell connection.•Highlights importance of additive manufacturing in fabricating bio-scaffolds. This article reports on the fabrication and evaluation of 3-D printed polyetheretherketone (PEEK) scaffolds with controlled macroporosity. Specifically, uniform macropore sizes ranging from 800 to 1800 µm by design were generated by varying processing parameters. It is expected that the 3-D printing ability to obtain customized macropores can help arriving at the optimum pore size in scaffolds to encourage bone regeneration. This study conclusively showed optimal cell adhesion and proliferation in scaffolds containing uniform pores of an average size of 800 μm. A construct containing a wide distribution of pores cannot come to this conclusion. In this context, the precision and reproducibility of additive manufacturing in scaffold fabrication play an important role.