Garlic is one of the most important cash crops cultivated by smallholder farmers throughout Ethiopia. However, due to inappropriate agronomic practices including intra-row spacing and clove size, the productivity of the crop is low in the country. Therefore, a field experiment was conducted during the 2019 main cropping season under rain feed condition to identify the optimum intra-row spacing and clove size for economical production of garlic in Addis Amba kebele of Lay Gayint district, South Gonder Zone, Ethiopia. Local garlic bulb obtained from farmers was used as test crop. The treatments consisted of three clove sizes namely large (2.0-2.5 g), medium (1.5-1.99 g) and small (1.0-1.49 g) and four intra row spacing (5, 7.5, 10 and 12.5 cm). The experiment was laid out in a randomized complete block design in a factorial arrangement with three replications. Data collected on phenological, growth and yield parameters were analyzed using SAS (Version 9.2) software. The results showed that days of emergence were highly significantly influenced by clove size while plant height was very highly significantly affected by intra-row spacing. The intra-row spacing and clove size interacted to influence bulb diameter, bulb weight, clove weight, marketable, unmarketable and total bulb yield. The highest marketable bulb yield of garlic was obtained from the combined treatment of medium and large size cloves with 7.5 and 10 cm intra-row spacing whereas, highest total bulb yields were obtained from the combined treatment of both medium and large-sized cloves with 5 and 7.5 cm intra-row spacing. However, the highest net benefit (723,205 Eth-Birr ha-1) and marginal rate of return were recorded from treatment combination of medium sized cloves and 10 cm intra-row spacing. Based on the results of the present study, medium sized cloves (1.5-1.99 g) planted at 10 cm intra-row spacing can be recommended for economic production of garlic in the study area and areas having similar agro-ecologies. However, since the results are limited to one season and location, it is advised to repeat the study in multi locations and seasons. Keywords: Bulb weight, bulb yield, garlic, plant population, productivity