A highly competitive environment is forcing sellers constantly using different marketing tools and strategies to win new clients and retain old ones in that way they can increase their profitability. Sales promotion is one of the best tools to attract new customers and retain old ones, including marketing activities by adding more value to the products for a limited period of time in order to stimulate consumer purchases and effectiveness of intermediaries. The purpose of this study is to investigate the effect of sales promotion on consumers’ buying behaviour. More specifically, the study sought to address the effect of contests and sweepstakes, price discount, coupons, point of sale materials on consumer buying behaviour in coca cola soft drink in Bahir Dar. For conducting the research Survey method was used to collect the data from coca cola consumers in Bahir dar city. A sample of 385 was studied and out of that 370 questionnaires were collected and analysed by applying descriptive and inferential statistical techniques using SPSS Version 25. The Pearson correlation coefficient used to show the magnitude and direction of association and is signifies that except coupons all independent variables (tools of sales promotion) and the dependent variable (buying behaviour) have strong positive relationships with one another. But coupons have a moderate positive correlation with predictor variables. The result shows that among the four sales promotion techniques: contests and sweepstakes with the value of 0.448, price discount with the value of 0.351, and point of sale materials with the value of 0.094 are the most effective variables for influencing consumer buying behaviour while coupons with the value of 0.078 are the least effective in influencing consumers buying behaviour. Therefore, it is recommended that managers and marketing specialists of the company should focus their efforts and invest more on these significant factors and improve the least effective factor which is coupons in influencing the buying behaviour of consumers.