This study aims to evaluate the feasibility of using the mussel as a bioindicator for the rapid detection of heavy metal (such as Cd, Pb, Hg, Ni, Cr, Cu, As, and Zn) fluctuations in aquatic environments and the sensitivity of the bioaccumulation of heavy metals in muscle tissues over time. The seasonal bioaccumulation patterns of heavy metals within Asian green mussels (Perna viridis), from Vietnamese coastal waters of Hai Phong were investigated using inductively coupled plasma mass spectrometry (ICP-MS). Additionally, the health risks from the consumption of P. viridis by local people were assessed. Mussels of varying sizes were sampled on a monthly basis between March (dry season) and July 2024 (wet season). The results revealed that the hepatopancreas had substantially higher concentrations of metals at all times relative to their corresponding muscle tissues, confirming its appropriateness as a bioindicator organ. The concentrations of heavy metals in mussels were recorded as significantly lower than the guideline levels, except for arsenic (As). Zinc (Zn) showed the highest concentrations, while mercury (Hg) had the lowest concentrations. There were strong seasonal and monthly differences, with peak levels of Pb, Cr, and As during the dry season, and high levels of Cs and Cu during the rainy season. It was found that the condition index, physiological factors, and shell size all had major impacts on the absorption of specific heavy metals. It was indicated that Pb, Cr, As, Cs, and Cu bioaccumulation are both biologically and environmentally responsive and can be used as proxies for environmental contamination, while the accumulation of these metals correlated with biological traits (shell length, weight, and CI), which is useful in modeling efforts. Health risk assessments using target hazard quotients (THQs) and the total hazard index (THI) identified Pb in the hepatopancreas as a primary contributor to the non-carcinogenic risk (THQ > 1), particularly during the dry season. The findings revealed the suitability of P. viridis, particularly hepatopancreatic tissue, as a short-term biomonitoring tool for detecting spikes and rapid fluctuations of certain heavy metals and assessing related human health risks in coastal aquatic systems.