New particle formation is globally one of the major sources of aerosol particles and cloud condensation nuclei. As primary emissions are a minor contributor to particle concentrations, secondary new particle formation processes are probably key in determining Antarctic aerosol number concentrations. However, our knowledge of new particle formation and its mechanisms in Antarctica is very limited. Here we study summertime open ocean and coastal new particle formation in the Antarctic Peninsula region based on both ship and station measurements. The rates of particle formation relative to sulfuric acid concentrations, as well as the sulfuric acid dimer-to-monomer ratios, were similar to those seen for sulfuric acid-dimethylamine-water nucleation. Numerous sulfuric acid-amine peaks were identified during new particle formation events, providing evidence that alkylamines were the bases that facilitated sulfuric acid nucleation. Most new particle formation events occurred in air masses arriving from the ice-covered Weddell Sea and its marginal ice zone, which are an important source of volatile sulfur and alkylamines. This nucleation mechanism is more efficient than the ion-induced sulfuric acid-ammonia pathway previously observed in Antarctica, and one that can occur rapidly under neutral conditions. This hitherto overlooked pathway to biologically driven aerosol formation should be considered for estimating aerosol and cloud condensation nuclei numbers in ocean-sea ice-aerosols-climate feedback models. New particles can form rapidly in Antarctica through the reactions of sulfuric acid and amines, suggest ship and station measurements around the Antarctic Peninsula.