Peak bone mass (PBM), attained between 20-30 years of age, influences osteoporosis risk. Trabecular bone score (TBS) is an emerging bone measure that complements clinically-preferred lumbar spine areal bone mineral density (aBMD). This cross-sectional study of 19 females ages 18-30 years examined the in vivo precision of TBS during years surrounding PBM. Spine dual-energy X-ray absorptiometry scans were performed in triplicate according to International Society for Clinical Densitometry guidelines. Percent coefficient of variation (%CV) for spine aBMD and TBS were compared using a paired t-test and relationships between %CV for both measures and body size measures were assessed using Pearson’s correlations. Both aBMD (%CV=0.88%) and TBS (%CV=0.89%) were highly precise and did not differ from one another (P=0.51) and measures of body size did not correlate with %CV for aBMD or TBS. In sum, TBS has similar in vivo precision as spine aBMD, which is not confounded by body size.