Pulsar Timing Arrays (PTAs) are exceptionally sensitive detectors in the nHz to uHz frequency window. While their primary purpose is to detect the stochastic gravitational wave background, they can also be used to search for new physics. Ultralight dark matter (ULDM), with mass between 10^{-23} eV and 10^{-20} eV, can generate a variety of different signals within the sensitivity window of PTAs. I will give an overview of the effects which have been studied previously, and then discuss new signals generated by variations in the fundamental constants. There are two main avenues to induce a PTA signal via variations in fundamental constants: changing the pulsar spin rate, e.g., by fluctutating particle masses, or shifting the reference clock. Using the standard analysis pipeline of the PTA collaborations, PTAs are shown to be competitive with atomic clock and torsion balance constraints for many ULDM models, especially those varying the electron and muon mass. Lastly, I will discuss how future PTAs may improve the sensitivity, and unique correlations in the signals which may further distinguish them from background.