This study investigated the concentrations and seasonal variation of selected heavy metals and total petroleum hydrocarbons (TPHs) in surface waters of five oil-dependent communities—Ngo, Ikuru Town, Oyorokoto, Okoroboile, and Asarama in Andoni Local Government Area, Rivers State, Nigeria. Water samples were collected during the dry and wet seasons and analyzed using Atomic Absorption Spectrophotometry (AAS) and Gas Chromatography-Flame Ionisation Detection (GC-FID), following APHA and USEPA guidelines. Mean concentrations of lead (Pb), cadmium (Cd), nickel (Ni), and TPHs exceeded both World Health Organisation (WHO) and National Environmental Standards and Regulations Enforcement Agency (NESREA) limits. TPH concentrations ranged from 3.11 ± 0.28 mg/L to 5.12 ± 0.45 mg/L, significantly surpassing the NESREA threshold of 0.05 mg/L. One-way ANOVA indicated statistically significant seasonal differences (p < 0.05), with higher pollutant levels observed during the wet season. Spatial analysis showed that Okoroboile and Ngo had the highest contamination levels, largely due to their proximity to oil spill sites and illegal refining activities. Strong correlations between TPHs and both Pb and Ni suggested common pollution sources. These findings raise serious ecological and public health concerns, highlighting the urgent need for remediation, environmental monitoring, and the provision of safe drinking water alternatives in the region