This study presents an investigation of the pyroelectric properties of single-crystal samples of triglycine sulphate (TGS) in 3D. The use of cubic samples and a suitable measurement setup made it possible to investigate the pyroelectric properties of TGS samples along the polar b axis and the mutually perpendicular directions to this axis. The measuring station was self-designed and constructed using a Keithley nanovoltmeter, a Rhode & Schwarz computer-controlled power supply, a GW INSTEK multimeter, a measuring chamber with Peltier cells, and a LabView custom user interface. Measurements of the pyroelectric response in 3D allowed us to conclude that the hydrogen bond between glycines G2-G3 may be strongly engaged in the phase transition in TGS, and is probably the trigger for the process. Our 3D investigation of the phase transition mechanism in single-crystal TGS is very promising in terms of research into the best pyroelectric materials for infrared thermal sensors.