A subsea chemical injection system and method for injecting chemicals into a hydrocarbon production assembly adjacent the seabed wherein a seawater volume flowmeter is utilized to measure seawater pumped through the system and a chemical subsea mass flowmeter is used to measure a chemical injected into the seawater, where the chemical subsea mass flowmeter measures the chemical at a pressure less than the seawater pumped through the system. Based on the chemical subsea mass flowmeter measurement, the flowrate of a chemical injected into the seawater can be adjusted to a predetermined setpoint corresponding to the flowrate of seawater pumped through the system. The chemical subsea mass flowmeter includes a Coriolis tube and chemical injection process pump housed within a pressure vessel. The subsea chemical injection system may be carried on a skid.