Tef is the most important staple cereal crop and is widely grown in Ethiopia, recognized as the center of origin and diversity in the country. Knowledge on genetic variability and trait associations is a key step in tef breeding programs. This study was conducted to evaluate the genetic variability, traits association, direct and indirect effect of yield related traits on grain yield of tef accessions. A total of 63 tef accessions collected from different parts of Ethiopia and one improved variety (Quncho, DZ-Cr-387) were evaluated for three qualitative and eighteen quantitative traits in 8x8 simple lattice design at Alem Ketema research sub-center during the 2023 main cropping season. The qualitative traits result showed that tef accessions collected from 2001-2500 m.a.s.l. had maximum H’ (0.86), whereas the lowest H’ (0.38) was obtained below 1500 m.a.s.l. The analysis of variance revealed significant differences among the tested accessions for all traits except thousand seed weight, indicating the existence of variability and potential for selection of the accessions for desirable traits. High GCV and PCV were observed for number of total tillers per plant, number of fertile tillers per plant, number of spikelets per panicle and flag leaf area. High heritability and high genetic advance as a percentage of mean were observed for days to heading (98.01%, 32.7%), days to physiological maturity (92.36%, 25.97%), plant height (90.9%, 26.97), panicle length (85.32%, 29.65%), culm length (86.92%, 27.57%), peduncle length (71.01%, 20.73%), number of spikelets per panicle (88.4%, 69.05%), number of primary panicle branches per main shoot (82.11%, 34.3%), flag leaf area (72.86%, 40.75%) and harvest index (81.48%, 28.93%) respectively. A positive and highly significant correlation was observed in genotypic level of grain yield and peduncle length (r=0.43), number of total tillers per plant (r=0.41), number of fertile tillers per plant (r=0.41), above ground biomass (r=0.35) and harvest index (r=0.76). A positive and highly significant correlation was observed in phenotypic level of grain yield and peduncle length (r=0.26), above ground biomass (r=0.62) and harvest index vii (r=0.67). Days to physiological maturity, plant height, number of primary branches per main shoot, flag leaf length, flag leaf width, above ground biomass and harvest index had positive direct effect on grain yield at genotypic level. At phenotypic level, positive direct effect on grain yield was exerted by days to heading, grain filling period, flag leaf area, above ground biomass and harvest index. This suggested that above ground biomass, grain yield and harvest index are the most important traits in selection of tef improvement. Cluster analysis grouped the accessions into five clusters consisting of 1 up to 27 accessions. The highest inter-cluster distance was noted between clusters I and III (372.87), while the lowest was between clusters IV and V (67.92). Principal components analysis revealed that three principal components with eigenvalues greater than one accounted for 82.8% of the total genetic variation among the tested tef accessions. The present results showed that the presence of wide range of genetic variations among tef accessions with desirable traits. This variation among traits could be used to develop varieties through selection and hybridization for tef grain yield improvement.