Kidney renal clear cell carcinoma (KIRC) and kidney renal papillary cell carcinoma (KIRP) are the most common RCC types. RCC has high immune infiltration levels, and immunotherapy is currently one of the most promising treatments for RCC. Collagen triple helix repeat containing 1 (CTHRC1) is an extracellular matrix protein that regulates tumor invasion and modulates the tumor microenvironment. However, the association of with the prognosis and tumor-infiltrating lymphocytes of KIRP and KIRC has not been reported. We examined the expression differences in multiple tumor tissues and normal tissues exploring TIMER, Oncomine, and UALCAN databases. Then, we searched the Kaplan-Meier plotter database to evaluate the correlation of mRNA level with clinical outcomes. Subsequently, the TIMER platform and TISIDB website were chosen to assess the correlation of with tumor immune cell infiltration level. We further explored the causes of aberrant expression in tumorigenesis. We found that level was significantly elevated in KIRP and KIRC tissues relative to normal tissues. expression associates with tumor stage, histology, lymph node metastasis, and poor clinical prognosis in KIRP. The level correlates to tumor grade, stage, nodal metastasis, and worse survival prognosis. Additionally, is positively related to different tumor-infiltrating immune cells in KIRP and KIRC. Moreover, was closely correlated with the gene markers of diverse immune cells. Also, high expression predicted a worse prognosis in KIRP and KIRC based on immune cells. Copy number variations (CNV) and DNA methylation might contribute to the abnormal upregulation of in KIRP and KIRC. In conclusion, can serve as a biomarker to predict the prognosis and immune infiltration in KIRP and KIRC.