The purpose of this research was to investigate the influence of swine-waste biochar (SB) on the early-age characteristics of cement pastes. Using a water/binder ratio of 0.28, SB modified cement pastes were analyzed using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), flow, and Vicat setting tests. Notably, SB reduced the flow and initial setting times of SB modified cement pastes. Due to its porous and negatively charged surfaces, capillary water was adsorbed into the pores of the carbonaceous SB and this reduced the flow of the SB modified cement pastes. Furthermore, it is suspected that the reductions in initial setting times may have been because with the addition of water to the dry SB/cement binder mix, chemical reactions between the calcium cations from Portland cement and carboxylate anions from SB resulted in the development of Calcium Polycarboxylate Salts (C-P-S). Improvements in the properties of SB could enhance its applications in rapid-setting and flow-reducing concrete.