Suspended sediment concentration (SSC) is an important indicator of coastal sediment dynamics and water quality. However, discontinuous in situ observations limit the characterization of long-term SSC variability. This study investigated the spatiotemporal variability of SSC and its associated environmental factors in Liaodong Bay (LDB) using MODIS satellite data from 2002 to 2026 and hourly GOCI-II observations. Spatially, a fan-shaped high-turbidity water body is observed, with SSC decreasing from nearshore to offshore areas. A distinct suspended sediment front occurs near the 10–16 m isobaths, while the boundary of the high-turbidity water body exhibits pronounced seasonal variations. Published in situ observations further reveal vertical variations in SSC. Temporally, hourly SSC variations are closely associated with tidal phases, while SSC is generally higher in winter than in summer. At the interannual scale, SSC exhibits an overall declining trend with quasi-periodic fluctuations of approximately 5–6 years. Topography plays a key role in shaping the spatial distribution of SSC, whereas the relative influence of environmental factors varies across timescales. At the monthly scale, sea surface temperature (SST), serving as an indicator of stratification and vertical mixing, and current velocity are the leading factors, with estimated relative contributions of 53.3% and 31.4%, respectively. At the interannual scale, wind speed (39.0%) and river sediment discharge (33.3%) become dominant. These findings provide insights into the multi-scale variability of SSC and its associated environmental controls, contributing to a better understanding of coastal sediment dynamics and supporting coastal management in semi-enclosed bays.