Little research is available directly comparing chelated mineral sources in a commercial dairy setting. The objective of this study was to determine effects of altering source of chelated trace minerals on lactation and reproductive performance in a commercial dairy herd. Six pens (3/treatment; 2,400 cows total; 6 mo duration) received the same isomineral diets, differing only in supplemental Cu, Mn, and Zn source. Supplemental Cu, Mn, and Zn were provided as metal methionine hydroxy analog chelate (MMHAC) or metal chelates of methionine and lysine (MMKC). Analyzed dietary mineral content (average ± SD) was 21.1 ± 1.9, 74.0 ± 8.1, and 78.0 ± 5.2 ppm Cu, Mn and Zn for MMHAC; 20.4 ± 2.2, 77.4 ± 12.3, and 79.6 ± 7.6 ppm Cu, Mn, and Zn for MMKC. Monthly DHIA milk yield, fat, solids nonfat, and SCC records were used to determine effect of chelated mineral source on lactation performance. Concurrently, breeding information was used to determine effect of source on reproductive performance. Data were analyzed using SAS/STAT software (Version 9.3; SAS Institute Inc., Cary, NC) with repeated measures as appropriate. Model included treatment, DIM and their interaction as fixed effects and pen within treatment as a random effect. No significant effects of treatment were observed for reproductive parameters including conception risk at any breeding (29.9 versus 29.4%; 95% CI 17.0, 47.0, MMKC and MMHAC respectively) and days open (106.8 vs. 107.8; 95% CI 99.9, 114.2). However, a significant treatment by time interaction was observed for milk yield (40.0 versus 39.8 ± 4.1, MMKC and MMHAC respectively; P = 0.02), fat % (3.45 versus 3.51 ± 0.20; P < 0.01), and solids nonfat % (8.77 versus 8.80 ± 0.10; P = 0.04). Failure to see differences in reproductive measures between treatments suggests little differences in the bioavailability of the evaluated chelated mineral sources. Observed increases in milk fat suggest additional value for MMHAC because of methionine hydroxy analog. Methionine hydroxy analog has previously been associated with increased milk fat. Together this data suggests that differing source of chelated trace mineral results in changes in lactation performance, particularly milk fat, over time that may significantly affect dairy farm revenue.