Background: The quality of life (QoL) of patients with end-stage kidney disease (ESKD) who undergo dialysis is a reliable predictor of their long-term survival. Hemodialysis is the most common form of kidney replacement therapy for ESKD, followed by peritoneal dialysis. This study aimed to identify the factors affecting QoL in ESKD patients treated with peritoneal dialysis (PD) or hemodialysis (HD) in Riyadh, Saudi Arabia. Methods: A cross-sectional study was conducted between June and July 2021 to assess the QoL of patients with ESKD who underwent peritoneal dialysis and hemodialysis. Patients who had been on dialysis for at least one year were included. The Arabic version of the Quality of Life Index–Dialysis (QLI-D) version III was used to measure the QoL. Results: A total of 210 patients completed the questionnaire. The overall QLI score was 21.73 ± 4.2, with subscales for health and functioning (20.35 ± 5.2), social and economic (20.20 ± 4.8), psychological/spiritual (23.94 ± 4.9), and family (24.95 ± 4.5). The QLI scores for PD and HD patients were 21.80 ± 4.4 and 21.72 ± 4.1, respectively. SOCSUB (p = 0.031) was significantly associated with group and income, whereas QLI (p = 0.003), HFSUB (p = 0.013), SOCSUB (p = 0.002), and PSPSUB (p = 0.003) were significantly correlated with group and years of dialysis. Conclusion: The study found that patients were most satisfied with their family, health and functioning, and social/economic subscales. Income and years of dialysis were found to be predictive factors of QoL. Overall, peritoneal patients in this study demonstrated a better QoL than HD patients.