Pol-${gamma}$-glutamic acid (${gamma}$-PGA), which is produced by microbial fermentation, is a biodegradable, hydrophilic and non-toxic biomaterial. ${gamma}$-PGA has many carboxyl groups that makes it a polyanionic biopolymer with swelling ability, biocompatibility and anticoagulant activity. On the other hand, few studies have examined the effect of ${gamma}$-PGA on the cellular activity of human umbilical vein endothelial cells (HUVECs). The present study evaluated the effects of ${gamma}$-PGA and fabricated ${gamma}$-PGA/PU composite films on the attachment and proliferation of HUVECs after treatment with microwave plasma at atmospheric pressure. The results confirmed that ${gamma}$-PGA is capable of increasing the proliferation and differentiation of HUVECs to form capillary tubes with enhanced alignment and organization. Moreover, the microwave plasma modified ${gamma}$-PGA/PU composite film was more hydrophilic and the surface roughness was enhanced. In addition, the attachment and proliferation of the HUVECs were increased by the plasma treatment. These results suggest that ${gamma}$-PGA and surface modified ${gamma}$-PGA/PU composite can be applied as bioactive and biocompatible materials in vascular tissue engineering but further testing of ${gamma}$-PGA and ${gamma}$-PGA/PU composite films will be needed to confirm the potential effects for use in vascular applications.