This study reports on levels of measurable trace metals in Halifax Harbour, Nova Scotia, in water samples, tissues of biomonitor species, and diffusive gradients in thin films (DGTs) – an in situ passive sampling device. Vase tunicates, Ciona intestinalis and blue mussels, Mytilus edulis, were selected as biomonitor species. The water, DGT, and tissue samples were collected from four sites in Halifax Harbour at five to six week intervals from June to October 2008. Mussels were collected from wharfs at two sites, and tunicates from the sites of DGT placement. In October 2008, tunicate samples from six smaller harbours in Nova Scotia were obtained for comparison of trace element content. All samples were analysed by inductively coupled plasma – mass spectrometry for determination of Mn, Mo, Cu, U, As, Co, Cd, Pb, and Ni concentrations. Halifax Harbour trace metal concentrations were established by complementary data from water samples (Mn, Mo, Cu, U, and U) and DGT samples (Co, Cd, Pb, and Ni). The data indicated a few significant localized variations and several temporal variations in the water column concentrations of some metals which, in the case of Mn and Cu, were attributed to storm drain effluents and rainfall events. Mytilus edulis bioaccumulated Co, Ni, Cu, Mo, Cd, and As to a greater extent than Ciona intestinalis, which accumulated higher concentrations of V. Bioconcentration factors for both biomonitor species indicate greater tissue concentrating capacity for Mn (800-4000), Cu (800-2000) and As (400-900), compared to Mo (40-75) and U (30-55). Concentration factors were similar in the two biomonitor species and, for M. edulis, appeared to increase with size. C. intestinalis in Halifax Harbour had among the lowest concentrations of As, Pb, Co, and Cu when compared to C. intestinalis in small harbours around Nova Scotia, possibly due to the placement of plate collectors at a greater distance from shore influences in Halifax Harbour.