Potato (Solanum tuberosum L.) production plays an important role in improving household income and nutrition and thereby contributes to food security. However the productivities of the potato remained low due to lack of appropriate agronomic recommendations. Afield experiment was conducted to evaluate the effect of seed tuber size and intra row spacing on growth and tuber yield of potato at Woramit Fruit and Vegetable Research Center, North West Ethiopia. The treatments consisted of three levels of seed tuber sizes in millimeter diameter (31-40,41-50,51-60) combined with three levels of intra row spacing in centimeter (20, 25 and 30) which were laid down in randomized complete block design with three replications. The collected data were analyzed using SAS (Version 9.4) software. The analysis of variance results indicated that number of main stem per hill, total tuber yield, marketable tuber yield, unmarketable tuber yield and medium-sized tuber yield significantly (p<0.05)affected by the interaction effects of tuber size and intra row spacing. The highest marketable tuber yield (36.78 t ha ) was recorded from 51-60mm seed tuber size with 30cm intra row spacing whereas the lowest marketable tuber yield (18.11 t ha -1 ) was recorded from 31-40mm seed tuber size with 20cm intra row spacing. The marketable tuber yield was positively correlated with main stem number per hill, total tuber number per hill, marketable tuber number per hill, average tuber weight, medium-sized, large-sized and total tuber yields whereas negatively correlated with unmarketable tuber number per hill, small-sized tuber and unmarketable tuber yield. Based on the results of the present study, large tuber size with wider intra row spacing gave the highest net benefit of 892836 ETB per hectare with a MRR of 212 %. Whereas the lowest net benefits 437465Eth-Birr/ha was obtained from the interaction effect of (31-40mm) with (20cm). Therefore based on biological and economic analysis, it was concluded that large size seed tubers economical feasible for -1potato production in the study areas and similar agro ecologies. However, the study was limited to single season, location and variety, further study over season location and variety is required to draw strong recommendation.