A 2-yr study was conducted at 2 locations to determine if supplementing beef heifers with dried distillers grains (DDG) as an energy source affected growth or reproduction. Spring-born crossbred heifers (n = 316) were blocked by age or sire and age and assigned randomly to DDG or control (dried corn gluten feed, whole corn germ, urea) supplement. Heifers received prairie hay in amounts sufficient for ad libitum intake and 0.59% of BW DDG or 0.78% of BW control supplement (DM basis). Supplements were formulated to be isocaloric, but protein degradability differed. Supplemental undegradable intake protein intake from DDG averaged 267 g/animal daily and reached 318 g/animal daily; control supplemental undegradable intake protein intake averaged 90 g/animal daily and peaked at 107 g/animal daily. Initial pubertal status was determined by 2 blood samples collected 10 d apart, and monthly BW were collected from November through January; then biweekly BW and blood samples were collected from February until May yearly. Heifers were synchronized with 2 injections of PGF2alpha 14 d apart; estrus was detected and heifers were artificially inseminated for 5 d and placed with bulls 10 d later. Conception and pregnancy rates were determined via transrectal ultrasonography. Initial age, BW, and BCS did not differ (P > 0.92) for control and DDG heifers. Final BW, ADG, and final BCS also were not affected (P > 0.31) by supplementation. Estimated age and BW at puberty did not differ (P > 0.23) between treatments, and the proportions of pubertal heifers did not differ at the initiation of the experiment (P > 0.82), at the beginning of the 14-d sampling intervals, or before synchronization. Estrus synchronization rate (75.9%), time of estrus, and overall pregnancy rate (89.5%) were not affected (P > 0.14) by treatment. However, a greater proportion (P = 0.008) of DDG than control heifers conceived to AI (75.0 vs. 52.9%), resulting in greater (P = 0.07) AI pregnancy rates for DDG heifers (57.0 vs. 40.1%). Body weight or BCS at pregnancy diagnosis did not differ (P > 0.52) between DDG and control heifers. Supplementing beef heifers with DDG during development did not affect age at puberty but improved AI conception and pregnancy rates compared with an isocaloric control supplement.