(1) Background: Hip arthroplasty (HA) is a surgery that replaces the damaged hip joint with an artificial implant called a hip prosthesis. The increase in life expectancy correlated with the population aging level, to which the increase in the number of prosthetic interventions among the young population is added, translates to the imperative need to analyze the quality of life beyond the immediate postoperative period. Strict adherence to an individualized rehabilitation program (IRP), and adapted to each patient, is followed by an improved quality of life. The main goal is the recovery of the patient with HA. This study was aimed to demonstrate that an IRP, represented by physical therapy associated with occupational therapy, improves the quality of life of patients with HA; (2) Methods: In this study, conducted between 2019 and 2021, 50 patients with HA were divided into two groups: study group—group A (25 subjects compliant with the IRP) and control group—group B (25 subjects, non-compliance with the IRP). To evaluate the two study groups, we monitored the evolution of the modified Harris hip score (mHHS) in both hips (arthroplasty hip (AH), contra lateral hip (CH)), for four months, respectively 30 days before the surgery (T0) and at 90 days after the surgery (T1); (3) Results: We notice significant differences in mHHS values at 90 days-T1 after surgery, both on AH in favor of subjects from group A vs. group B (p = 0.030) and on CH, where mHHS values were statistically higher in group A compared to group B (p < 0.001). The results of our study outline at T1 moment, both on the AH (p = 0.030) and on the CH (p < 0.001), the fact that mHHS values were statistically higher in patients included in group A compared to group B. In terms of the results for mHHS, comparing AH with CH, it is noted that the number of subjects who had a good or excellent mHHS result in group A versus group B is statistically significant in the case of CH (group A: 23 (92%) vs. group B: 11 (44%), p = 0.039); (4) Conclusions: The study reveals clear advantages of HA in both hips, both in subjects who complied with the IRP and those who did not comply; the higher therapeutic benefits of IRP are outlined at the level of CH compared to AH; in patients who comply with the IRP, the mHHS parameters that have improved in both CH and AH are pain, leaning, and shoes and socks activities; in addition, limping was reduced in CH.