<p>Mussel monitoring results in marine environments can be affected by both biotic and abiotic factors regarding cesium (Cs, relating to ¹³⁴Cs and ¹³⁷Cs) bioaccumulation. The reliability of field monitoring data may be compromised, as accurate models for transfer require realistic measurements of kinetic parameters. This study investigated the impact of abiotic (e.g., Cs concentration in water, temperature, salinity, and pH) and biotic factors (condition index, shell size, and weight) on Cs uptake, distribution, and excretion in two Asian green mussel organs. Concentrations of Cs were determined using ICP-MS (Agilent 7900). The result showed preferential accumulation in the hepatopancreas, highlighting digestive and metabolic organs as key bioaccumulation sites. Higher Cs concentration and temperature significantly increased Cs accumulation in the mussels. However, as pH and salinity spiked Cs uptake dropped, indicating a significant impact on Cs absorption as well. As the condition index rose and the shell size decreased, the concentration of Cs increased, while weight had no discernible impact. The Cs excretion in Asian green mussels was characterized by an initial rapid loss of Cs during the first three days. By day 11, clearance was greater than 90%, Cs excretion slowed down and was almost complete by day 70. This excretion pattern suggests a potential drawback in using them for monitoring short-term contamination events. This study contributes essential baseline data for applying <i>Perna viridis</i> as a biological indicator in marine radiological monitoring programs. The findings are particularly valuable for Vietnam, where systematic biomonitoring of radioactive pollutants in coastal environments remains limited.</p>