<p>Fe-Ni alloy electrodeposits were investigated as a synthetic means to suppress fatigue crack growth in ASTM A36 carbon structural steel. The effectiveness of this technique in suppressing active fatigue crack growth was evaluated. Under the conditions of the experiment, results demonstrated complete arrest of actively growing fatigue cracks for up to 285,000 load cycles following a single Fe-Ni electrodeposition treatment. Additionally, up to two repeated electrodeposition treatments were also effective at delaying crack growth, with effectiveness diminishing as the crack length grew and the stress intensity factor range correspondingly increased. Fatigue crack reinitiation life following arrest was quantified and modeled using a Huang-modified form of the Correia equation. Electrodeposit composition and surface morphology were examined to assess uniformity, validate the electrodeposition composition control method, and support the interpretation of the treatment’s influence on fatigue crack growth behavior.</p>