Besides Everwood, Niznik's television roles include guest roles on Dr. Quinn, Medicine Woman, Profiler, Sliders, JAG, Frasier, Epoch, Star Trek: Enterprise, Traveler, and Diagnosis: Murder, in addition to being a series regular on the mid-1990s action drama Vanishing Son and the 2007 drama Life Is Wild. She has also appeared in the films Star Trek: Insurrection and Exit to Eden.