In current study, a new polyethyleneimine (PEI)-modified attapulgite material was prepared serving as a solid support in matrix solid-phase dispersion for the extraction and determination (by atomic absorption spectrometry) of cadmium in seafood products. The major factors affecting PEI grafting were optimized using various PEI amounts and molecular weights. Parameters pivotal to MSPD extraction efficiency, like: pH, volume of eluting solvent, and the sorbent mass-to-sample ratio were investigated. Quantitative recoveries were achieved with 0.21 g of fish sample, 0.13 g of PEI-modified attapulgite dispersing agent, and 50% HNO₃ eluting solution. The limit of detection and the limit of quantification were found to be 2.5 and 8.3 μg kg⁻¹ for cadmium in surimi samples, respectively. The recoveries were in the range of 89.2–100.1%, with RSDs ranged from 3.0% to 7.9% (n = 5). When compared to the method stipulated by the Chinese National Standard GB 5009.15-2014, the newly developed MSPD provides comparable accuracy and even better repeatability for the analysis of the cadmium in real seafood samples.