To investigate the effect of temperature on the immobilization of phosphorus (P) and arsenic (As) by lanthanum-modified bentonite (LMB) at the sediment-water interface (SWI) and determine the optimal remediation temperature for maximizing its efficacy, laboratory-scale simulation experiments were performed using SWI samples collected from eutrophic shallow lakes. Microelectrode profiling, high-resolution porewater sampling, and inductively coupled plasma mass spectrometry (ICP-MS) were employed to characterize the spatiotemporal dynamics of dissolved oxygen (DO), pH, iron (Fe), manganese (Mn), and dissolved organic matter (DOM) under three controlled temperature conditions (10?℃, 20?℃, and 30?℃). Concurrently, high-precision analytical methods were utilized to quantify the speciation and distribution of dissolved P and As. Results showed that elevated temperatures decreased DO concentrations, increased pH values, and elevated DOM content in the SWI. These changes facilitated the formation of anaerobic conditions, promoting the reductive dissolution of Fe and Mn oxides and thereby enhancing the release of dissolved P and As. The immobilization efficiency of LMB was clearly temperature-dependent, with maximal efficacy observed at 20?℃. At this temperature, the concentrations of dissolved P and As decreased by 85.97% and 41.43%, respectively, on day 7, and remained significantly suppressed on day 50, with reduction rates of 82.10% and 20.35%. Furthermore, LMB application facilitated the transformation of mobile fractions of P and As into more stable chemical forms in the sediment matrix. Specifically, at 20?℃, the proportion of stable P increased from 48.55% to 51.05%, whereas that of stable As rose from 62.20% to 68.92%. This study demonstrates that the effectiveness of LMB in mitigating the release of P and As at the SWI is strongly temperature-dependent. The optimal restoration temperature of 20?℃ identified by the study can be applied to address endogenous pollution in shallow lakes of temperate and subtropical regions during the spring and autumn seasons when water temperatures are suitable. Keyword: Temperature; lanthanum-modified bentonite; sediment-water interface; phosphorus; arsenic