Neither the inheritance of condensed tannins (CT) in tannin-positive birdsfoot trefoil (Lotus corniculatus L.), nor the quantitative genetic analysis of CT concentration in a forage legume have been previously reported. The objective of this study was to determine the inheritance of CT concentration in tannin-positive birdsfoot trefoil. High-, medium-, and low-tannin parents were selected from NC-83 birdsfoot trefoil germplasm and intercrossed in two independent six-parent diallel sets to generate progenies for quantitative genetic analyses. Maturity, herbage yield, leaf fraction (LF) and CT concentration were analyzed for 1067 individual F1 plants from 30 progenies in both diallel sets. Mean CT concentrations of the 30 progenies ranged from 6.1 to 93.4 g catechin equivalent (CE) kg−1 DM. General combining ability (GCA):specific combining ability (SCA) ratios of 0.93 and 1.0 were observed for CT concentration in both diallel sets, at or near the theoretical maximum of unity, indicating a predominance of additive genetic effects for CT concentration. Specific combining ability effects were detected in one diallel set where 3 of 15 progenies exhibited significant SCA effects. The evidence from this study indicated that CT concentration in birdsfoot trefoil was controlled primarily by additive genetic effects. Key words: Birdsfoot trefoil, condensed tannins, forage legume, inheritance, Lotus corniculatus, quantitative genetics