Hemp seed meal (HSM) has the potential to serve as a replacement protein feed for horses. The goal of this project was to assess the protein digestibility and acceptability of HSM in equine diets. Four feed concentrates containing 0% (control), 10%, 20%, and 40% HSM were tested. Horses were randomly assigned to the four feed concentrates over four 7-day periods in a 4 × 4 Latin square design. Horses were offered a first-cutting, mixed orchardgrass-timothy hay at 1% of body weight (BW; as-fed) and the feed concentrate at 0.4% BW (as-fed) in the morning and evening and were turned out to a winter pasture for approximately 7.5 hours per day. Horses were adapted to their respective feed concentrate from days 1 to 5 followed by fecal sample collection on days 6 and 7 of each period. Protein digestibility was measured using both lignin and acid-insoluble ash (AIA) as internal, indigestible markers. Whole-diet (hay + concentrate) protein digestibility, feed concentrate intake, hay intake, fecal consistency, and weight change were assessed. No refusals of feed concentrates occurred across treatments. No differences were observed for any of the measured variables between the HSM treatments and the control. Digestibility values measured using AIA appeared overestimated, potentially due to soil contamination, whereas digestibility values measured using lignin fell within reported ranges for horses consuming grass hay and feed concentrates. The results demonstrate that HSM inclusion up to 40% does not affect feed concentrate intake, fecal score, and whole-diet protein digestibility, indicating that HSM is an acceptable feed ingredient for horses and may replace soybean meal as the primary protein source.