The objective of our study was to determine the effects of altering the ratio of stearic (SA) and oleic (OA) acids in supplement fat blends on fatty acid (FA) digestibility and production responses of dairy cows. Eight multiparous Holstein cows (157 DIM ± 33) were randomly assigned to treatment sequence in a replicated 4 × 4 Latin square design with 14-d periods. The treatments were a non-FA supplemented control diet (CON), and 3 diets incorporating 1.5% DM FA supplement blends containing 50% SA and 10% OA (50:10), 40% SA and 20% OA (40:20), or 30% SA and 30% OA (30:30). FA blends were balanced to contain ~30% palmitic, 5% linoleic, and < 0.5% linolenic acids. FA supplements replaced soyhulls in the CON diet. The statistical model contained the random effect of cow within square and the fixed effects of period, treatment, and their interaction. Pre-planned contrasts included CON vs. fat supplementation and the linear and quadratic effects of increasing OA. Results in the text are presented in the following order: CON, 50:10, 40:20, and 30:30. There was no effect of treatment on DMI (P = 0.91). Compared with CON, FA treatments increased milk yield (43.0, 44.7, 45.7, 45.2 kg/d; P < 0.01), ECM (43.4, 45.5, 45.8, 44.9 kg/d; P = 0.02), and fat yield (1.49, 1.58, 1.58, 1.55 kg/d; P = 0.01) and tended to increase milk protein yield (P = 0.10). Compared with CON, FA treatments had no effect on the yield of de novo milk FA (P = 0.35), decreased mixed milk FA (P = 0.04), and increased preformed milk FA (P < 0.01). The increase in preformed FA yield was predominantly due to FA treatments increasing the yield of OA in milk (218, 250, 264, 264 g/d; P < 0.01) compared with CON. Increasing OA did not affect milk yield (P = 0.63), milk fat yield (P = 0.33), or milk protein yield (P = 0.61). Increasing OA in FA treatments linearly decreased the yield of de novo (416, 420, 411, 391 g/d; P = 0.03) and mixed (534, 573, 560, 544; P = 0.05) milk FA, but did not affect the yield of preformed FA (440, 493, 510, 514; P = 0.12). In summary, feeding FA supplements containing SA and OA increased milk yield, ECM, fat yield, and preformed FA in milk compared with a no added fat control diet.