In this research, Vertical Electrical Soundings (VES) were conducted along the coastal region of Miri City, East Malaysia for two different seasons to determine the spatial and temporal variation of aquifer vulnerability through Geographic Information System (GIS). VES data was processed in IPI2Win software and curve matching method was adopted to determine the predominance curve types in the study area. The corrected data were used to create spatial maps for resistivity and thickness for each layer through ArcGIS software. Pseudo cross-sections were produced to identity the lithological variance and the movement of saline groundwater plumes. Dar Zarrouk parameters such as longitudinal conductance (S) and transverse resistance (T) were also calculated and spatial maps were prepared to differentiate freshwater and saline water aquifers in the study area. From the results, it was found that the dominant curve types identified in the study area are Q type (24%) and QH type (28%) during the Northeast monsoon (NEM); whereas QH type (19%) and QHKH type (18%) are identified during the Southwest monsoon (SWM). The significant resistivity values that indicate the saline water intrusion (SWI) are 0.49–47.6 ohm.m and 4.34–40.2 ohm.m, which was identified from the northern and southern parallel pseudo cross-sections. Overall, the study reveals that the intensive SWI occurred during SWM, compared to NEM. SWI was observed with low resistivity at a deeper depth of 20 m on the northern side of the study area. The southern urban area of Miri City is continuously prone to infiltration of brackish water at shallow depth caused by anthropogenic activities.