Objective This study aimed to determine the prognostic factors of progression-free survival (PFS) and overall survival (OS) in non-nephrectomized patients with synchronous metastatic renal cell carcinoma (mRCC) receiving first-line vascular endothelial growth factor (VEGF)-targeted therapy or immunotherapy. Methods Of 70 patients, 57 (81.4%) were treated with targeted therapy, including 5 (7.1%) with previous immunotherapy and 13 (18.6%) with immunotherapy only. The medical records of patients were retrospectively reviewed and analyzed to determine factors of PFS and OS using the Cox proportional hazards model with a statistical significance p-value <0.05. Results The median treatment and follow-up periods were 3.9 and 30.9 months, respectively. Disease progression was reported in 90.0% of patients, with an objective response rate and clinical benefit rate of 26.1% and 76.8%, respectively. The lung (77.1%) was the most common site of metastasis. Multivariable analysis showed that poor Heng risk (hazard ratio [HR]: 2.37) and liver metastasis (HR: 2.34) were significant prognostic factors for PFS, and female sex (HR: 2.13), poor Heng risk (HR: 3.14), and liver metastasis (HR: 2.78) were significant prognostic factors for OS (p < 0.05). A subset analysis of risk factors among patients without previous history of immunotherapy also showed poor Heng risk (HR 2.92 and HR 4.24 for PFS) and liver metastasis (HR 2.87 and HR 4.81 for OS) as significant factors for both PFS and OS (p<0.05). Conclusion Poor Heng risk, sex, and liver metastasis were associated with survival outcomes after first-line systemic therapy in patients with non-nephrectomized synchronous mRCC.