Peyronie’s disease (PD) is a condition of penile connective tissue affecting up to 10% of men worldwide. In the complexity of its management, nonsurgical treatments, such as intraplaque injections, are gaining attention. The current literature shows data on the efficacy of intraplaque injections of hyaluronic acid (HA) mainly in acute-phase PD. However, data on injections of HA in stable-phase PD are lacking. Data for this retrospective study were derived from a prospectively maintained database of private patients presenting at a private medical practice affiliated to the University of Naples “Federico II” (Naples, Italy) with stable-phase PD between January 2020 and March 2023. Patients underwent a standard protocol of three injections, each administered at a two-week interval. During the intervals, patients performed vacuum device therapy, penile stretching, and modeling exercises. All patients compiled the Peyronie’s Disease Questionnaire (PDQ) and Global Assessment of Peyronie’s Disease (GAPD) at baseline and 2 weeks after the third injection. A penile Doppler ultrasound was performed 2 weeks after the last injection to record the final curvature. Overall, we recruited 62 patients with stable-phase PD and a mean (±standard deviation [s.d.]) curvature of 52.7° (±9.7°). After 6 weeks, eight (12.9%) patients did not experience any curvature improvement. The remaining 54 patients had a final mean (±s.d.) curvature of 40.3° (±9.1°) with P < 0.001, compared to that before treatment. We found improvement in all PDQ domains (all P ≤ 0.01), and 50 (80.6%) patients reported subjective improvement of the penile curvature according to the GAPD. In conclusion, we demonstrated that after three injections of HA administered according to the adopted protocol, patients with stable-phase PD could experience significant improvements in penile curvature, and physical and psychological consequences of the disease without significantly relevant side effects.