Objective To investigate the influence of peri-implant keratinized mucosa width on the health of peri-implant soft and hard tissues after restoration for 12 months. Methods Forty Straumanns' implants were planted in 25 patients. After the final prostheses were restored, the keratinized mucosa width (KMW) was measured in the middle buccal of the implants. Implants were divided into two groups: KMW≥2 mm and KMW<2 mm (n=20). Radiographs for bone loss were taken and bleeding on probing (BOP), plaque index (PLI), gingival index (GI), probing depth (PD) and mucosal recession were measured at the restoration day (baseline), 6 and 12 months after restorations. Results After restoration for 12 months, PLI and BOP scores of both groups were significantly higher than those of baseline (P<0.05), and plaque index values of KMW<2 mm group were significantly higher than those of KMW≥2 mm group (P<0.05). The mucosal recession around implants of KMW<2 mm group was obvious. The differences of PD and marginal bone loss around implants of two groups were not statistically significant (P>0.05). Conclusion The keratinized mucosa may have positive effects on plaque control and mucosal recession around dental implants, but the exact effect needs further study and longterm observation.