Many factors influence the low productivity of carrot. Improper irrigation management and undetermined plant population is the major once among others that influence the production and productivity of carrot in Ethiopia. Therefore, a field experiment was conducted to study the effects of irrigation interval and number of rows per bed on growth, yield, and yield components of carrot during the 2017 irrigation season at Koga Irrigation Scheme. The treatments consisted of three irrigation intervals (4, 7 and 10 days) and three numbers of rows per bed (2, 3 and 4) combined with spilt plot design with three replications where the irrigation intervals were assigned as main plots and the number of rows per bed as subplots. Phenological, growth, yield, and yield related parameters of carrot, variety Nantes, were collected timely as per their respective standard procedures. Variance analysis of the data was done using SAS Software version 9.0. Except the main effect of rows per bed on root diameter and unmarketable yield, the main as well as the interaction effects of irrigation interval and rows per bed significantly affected most of the tested parameters of carrot. Three rows per bed in seven days irrigation interval and four rows per bed in four days irrigation interval recorded the highest marketable carrot root yields with 23.57t ha-1 and 23.25 t ha-1, respectively. Moreover, a combination of seven days irrigation interval with three rows per bed gave the highest net benefit of carrot. However, a combination of ten days irrigation interval with three rows per bed recorded the highest marginal rate of return which can be recommended for the study area and areas with similar agro-ecologies. Nevertheless, it is recommended to repeat the experiment on wider scale in different agro-ecologies for wider utilization. Key words: Marketable yield, Nantes, population of carrot, root diameter, root length