Polylactic acid (PLA) fillers are widely used for cosmetic volume augmentation. But, no study has evaluated the use of PLA filler in penile augmentation (PA No. 4). We evaluated the efficacy and safety of a newly developed PLA filler for PA during a 18-month follow-up period. A total of 23 healthy adult men were prospectively enrolled between June and November 2012. Penile girth was measured at proximal-, mid- and distal-shaft at baseline, 3, 6, 12 and 18 months following injection. Subjects' satisfaction was assessed with visual analogue scale (VAS). Adverse events (AEs) were also reported. Mean injected volume was 20 ml. The circumference of proximal-, mid-, and distal-shaft increased by a mean of 2.2±0.2, 2.7±1.0 and 2.7±1.0 cm at 3 months, respectively (each P<0.001). No significant differences were noted in girth circumference between 3 and 18 months post-injection (each P>0.05). VAS score increased from 51.6±14.7 at baseline to 64.8±19.3 and 74.3±14.6 at 3 and 6 months, respectively (each P<0.05). Six cases of mild, transient treatment-emergent AEs were reported in 5 subjects. Serious AEs were not reported. In conclusion, penile injection of a newly developed PLA filler led to significant penile augmentative effects for up to 18 months and was well tolerated without serious AEs.