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We investigated whether diet conditioning (a.k.a., diet training) would increase cattle use of spotted knapweed (Centaurea stoebe) and increase the efficacy of targeted cattle grazing to suppress this invasive perennial forb. We applied targeted cattle grazing for three consecutive years to spotted knapweed-infested rangeland in northwestern Montana, USA. Cattle simultaneously grazed within six, 1.3-ha pastures at a moderate stocking rate and low stock density during late July-early August (spotted knapweed in late bud-early flower phenotypic stage). Three yearling Angus heifers grazed within each pasture for 15 days in 2013 and 2014 and 12 days during the 2015 drought. Each year, three pastures were grazed by unconditioned cattle, whereas three pastures were grazed by cattle conditioned to eat spotted knapweed. Immediately preceding each year�s targeted grazing trial, cattle in the conditioned treatment were systematically introduced to novel and nutritious foods (cracked corn, rolled barley, wheat bran, and others) for four days, followed by six days in which cattle were gradually introduced to spotted knapweed to encourage its consumption during the grazing trial. Otherwise, cattle in our study had no previous experience eating spotted knapweed before arrival at our study site. Our results revealed that diet conditioning did not affect any of the response variables we sampled (P�> 0.10). Cattle diets averaged 10% spotted knapweed and 38% graminoids; forage utilization averaged 38% and 56% for spotted knapweed and perennial graminoids, respectively; neither conditioned cattle nor unconditioned cattle preferred eating spotted knapweed (preference index = 0.45); and cattle grazing averaged 85% removal of spotted knapweed buds, flowers, and seed-heads. After three years of treatment, targeted cattle grazing reduced spotted knapweed plant density 66%, but diet conditioning provided no additional benefit.