Lower Paleozoic samples from Truro Island, Arctic Canada, are assessed for hydrocarbon source rock potential, thermal maturity and paleoenvironment using Rock-Eval pyrolysis, gas chromatography-mass spectrometry (GC and CC-MS) and incident light microscopy. The Upper Ordovician Irene Bay Formation does not contain potential hydrocarbon source rocks. Only minor chitinozoans, graptolites and coccoidal, bacteria-like macerals are present in these rocks. Thermal maturity of the Cape Phillips Formation equates to an average vitrinite reflectance of near 0.67 %Ro. The Upper Ordovician to Upper Silurian Cape Phillips Formation has good source rock potential (Type II-I kerogen) with total organic carbon (TOC) contents ranging from 0.23% to 5.57%. Amorphous organic matter is dominant in this formation hosting agglomerations of coccoidal bacteria-like and degraded filamentous alginite macerals. Several of the Cape Phillips samples contain abundant fluorescing hydrocarbon fluid inclusions with variable lambda max (nm) properties. The sterane distributions of most of the Cape Phillips samples show a predominance of C-29 over C-27 steranes suggesting contribution from different types of algae. Relatively high hopane to sterane ratios suggest greater microbial reworking during early diagenesis, which is in agreement with the dominance of amorphous macerals. The Lower Devonian Disappointment Bay Formation contains Type II-I kerogen with good potential to generate hydrocarbons (TOC up to 2.41%). Macerals are dominated by bitumen, alginite-bitumen transition macerals and stromatolitic filamentous alginite. High production indices, high extract yields, and maceral reflectance and fluorescence indicate the formation is in the early stages of hydrocarbon generation (vitrinite %Ro near 0.55) via prolific early bitumen generation. Several populations of fluorescing hydrocarbon fluid inclusions, based on lambda max, also occur in the Disappointment Bay Formation. Saturate fraction gas chromatograms (SFGCs) and the m/z 191 and m/z 217 mass fragmentograms indicate extensive biodegradation. A slight predominance of C-29 over C-27 steranes with much lower amounts of C-28 steranes results from a marine algal origin fnr the organic matter.