Abstract: Primary productivity and selected relevant associated physico-chemical parameters in the euphotic zone of Lagos Harbour, a tropical Harbour was monitored at NIOMR Jetty station (Latitude 6º 25´ 14, 88º N, Longitude 3º 24´ 24, 42º E) on a monthly basis from October, 2012 to March, 2013. Air and surface water temperature ranged from 23.5⁰C to 28⁰C and between 27 ⁰C and 30⁰C respectively. Alkaline pH ranged (7.81 to 8.45). Brackish salinity varied from 6.2 to 35.4PSU while Electrical conductivity minimum and maximum values were 11200 and 53300µS/cm respectively. Moderate dissolved oxygen ranged between 5.0mg/l and 6.4mg/l, slightly lower than 6.8mg/l standard suggested by FEPA. Total dissolved solid ranged from 7504 to 35711mg/l while Low Alkalinity varied between 12 and 20mg/l. Rainfall minimum and maximum values were 8.8 and 229mm respectively. Gross primary production (GPP) varied from 0.22 to 0.46gC/m2/day.