The level of heavy metals in water, sediment, water hyacinth (Eichhornia crassipes) and frillfin goby (Bathygobius soporator) from Ologe Lagoon and its tributaries were monitored because of the importance of the water bodies to the socio-economic well-being of the rural population. Physico-chemical parameters and selected heavy metals (Fe, Zn, Cu, Pb and Cd) contents of water, sediment, E. crassipes and B. soporator from six sampling stations in Ologe Lagoon were measured monthly from February to November, 2015. The range of concentration of heavy metals in sediment are: Fe (454±112-2756±1213mg/kg), Zn (3.89±3.08-18.7±6.83mg/kg), Cu (7.68±5.65-36.8±16.9mg/kg), Pb (6.24±2.56-11.2±4.45mg/kg) and Cd (0.42±0.170.92±0.42mg/kg). Heavy metal concentration in E. crassipes were 68.5±16.5-987±86.8mg/kg, 13.2±6.40-162±46.2mg/kg, 0.56±0.25-6.54±1.45mg/kg, 5.06±2.41-12.2±4.71mg/kg and 0.28±0.22-1.21±0.49mg/kg for Fe, Zn, Cu, Pb and Cd respectively. The concentrations of heavy metals in the muscle of B. soporator in wet season were: Fe, 8.30±2.29 mg/kg; Zn, 0.78±0.28 mg/kg; Cu, 16.20±6.20 mg/kg; Pb, 2.21±0.33mg/kg; Cd, 0.16±0.05mg/kg while in dry season, they were: Fe,
27.19±7.28 mg/kg; Zn, 24.47±6.27 mg/kg; Cu, 0.18±0.16 mg/kg; Pb, 1.72±0.07mg/kg; Cd, 0.19±0.03mg/kg. Hardness and turbidity showed significant (p<0.05) spatial variation. Concentrations of Fe, Zn and Cu in sediment varied significantly (p<0.05) among the sampling sites but Pb and Cd did not. The heavy metal content of water hyacinth from the six sampling
stations exhibited significant (p<0.05) spatial variation except Cd. The concentrations of Fe, Zn and Cu in B. soporator were significantly (p<0.05) affected by season but Pb and Cd were not. Although only Pb exceeded the FAO/WHO maximum permissible limits in the tissue of B. soporator, regular monitoring of Ologe Lagoon is advocated in order stern further deterioration of the ecosystem and to protect the rural population that depend on it for sustenance.