This study was focused to assess the contamination status of heavy metals in sediments, and human health risks associated with fish consumption from western Nigeria offshore in the Gulf of Guinea. Triplicate samples of demersal marine fish species and sediments were collected from five stations (fishing ground) and analysed for heavy metals [mercury (Hg), cadmium (Cd), and lead (Pb)] and metalloid [arsenic (As)] using ICP-OES (inductively coupled plasma optical emission spectrometry) adopted USEPA 200.7 standard method. The metals/metalloid concentrations in demersal fish species and sediment fell below the FAO/WHO permissible limits and sediment quality guidelines (SQG) [probable effect level (PEL) and threshold effect level (TEL)]. The ecological indices [probable contamination index (PCI), mean effect level quotients, newly modified hazard quotient (mHQ), and hazard quotient (HQ)] revealed low contamination level of heavy metals in sediment. The hazard index (HI) of metals in fish species associated with human health fell below the recommended threshold of 1 with no significant health risk to the consumers. The target cancer risk (TCR) of Cd and Pb in the fish species were below the regulation range of 1.0 × 10−6 to 1.0 × 10−4 set by the USEPA. The cluster analysis revealed two clusters. Cluster 1 (C1) showed that Cd was significantly accumulated in the sediment. Cluster 2 (C2) showed significantly low bioaccumulation of Hg, Cd, Pb, and As in fish species across all stations. The ecological and health risk assessment indices generally established low potential adverse effect on demersal marine fish species due to the overall low ecological severity risk associated with heavy metals/metalloids in sediment. Hence, consumers of fisheries resources from western off Nigeria coast are relatively safe from being exposed to any non-carcinogenic and carcinogenic health risk.