Anthracnose, caused by Colletotrichum truncatum, is a major disease of lentil (Lens culinaris) on the Canadian prairies. Age-dependent resistance to the pathogen was elucidated on (i) the partially resistant line ‘CDC Redberry’ compared with both resistant (LR59-81) and susceptible (‘Eston’) lines at different ages across the life cycle of the plant, and (ii) a range of lines with varying resistance at key ages, using both races of the pathogen (races Ct0 and Ct1). CDC Redberry appears moderately susceptible when inoculated at a young age and is more resistant when inoculated 19 to 26 days after planting. The highest disease levels were observed on the oldest plants studied (inoculated at podding stage, 47 days after planting). This pattern of age-dependent resistance in CDC Redberry was the same after inoculation with either race of the pathogen and indicated that the best differentiation occurs when plants are inoculated at the podding stage. ‘CDC Robin’ showed consistent separation between races at all ages but the most substantial differences were observed on plants inoculated at 47 days of age. Resistant lines LR59-81 and VIR 421 were relatively unaffected by age or by race of C. truncatum compared with partially resistant and susceptible lines. Overall, results suggest that differentiation between resistant and susceptible lines is optimal using older, adult-phased plants.