Few options exist for calibration of transducers at infrasonic frequencies. A variable frequency infrasonic pistonphone is one option for calibration; however, thermoviscous effects can decrease the accuracy of calibrations made using an infrasonic pistonphone. An infrasonic pistonphone is developed that produces calibration signals between 0.001 and 30 Hz. To decrease calibration uncertainty due to thermo-viscous effects, the pressure inside the constructed pistonphone chamber is calculated using Rott’s continuity and momentum equations, readily accepted equations that model thermo-viscous effects in enclosures. The pressure response of the pistonphone chamber is measured, and compared with the pressure predicted by a model incorporating Rott’s equations. Example calibrations and thermo-viscous effect corrections are conducted. Results show an increase in calibration accuracy, and demonstrate the potential usefulness of the pistonphone design for the calibration of acoustic transducers at infrasonic frequencies.