Introduction: Exclusively breastfed infants experience more rapid growth in the first 6 months than other infants. This is because exclusive breastfeeding offers infants a food source (breast milk) that is packed with essential nutrients, immune boosting elements, and other biologically active compounds crucial for optimal growth and development. However, owing to the increasingly expanding market for breast milk substitutes, the duration of breastfeeding is declining worldwide. Objective: To assess the determinants of infant formula feeding among mothers of infants aged 0-6 months in Debre Berhan city, 2023 Methods and Materials: Between the 10th and 20th of May 2023, a total of 656 mothers were selected by employing a multistage sampling technique. The data were collected using a semi structured questionnaire, and the results are presented using frequencies, percentages, and graphs. In addition, bivariate and multivariable logistic regression models were employed to identify predictors of infant formula feeding. According to the multivariable logistic regression models, variables with a p value less than 0.05 were considered statistically significant predictors of infant formula feeding, and the adjusted odds ratio (AOR) was used to indicate the degree of association between the predictor variables and infant formula feeding. Results: According to our study, 39.7% of the mothers in Debre Berhan city practiced infant formula feeding. In addition, mothers who were aged 25 to 34 years [AOR = 2.68, 95% CI: 1.26, 5.70] or 35 to 45 years [AOR = 4.74, 95% CI: 1.86, 12.1], primipara [AOR = 4.48, 95% CI: 2.69, 7.45], had received antenatal care (ANC) [AOR = 2.26, 95% CI: 1.74, 5.06], had delivered through the caesarian section (C/S) [AOR = 4.28, 95% CI: 2.12, 8.65], not aware of the risks of infant formula feeding [AOR = 7.26, 95% CI: 4.09, 12.85], or who had initiated breastfeeding after an hour of birth [AOR = 5.27, 95% CI: 3.14, 8.85] were more likely to feed their babies infant formula. Conclusion: Our findings suggest a high prevalence of infant formula feeding in Debre Berhan city, and the majority of the factors that lead to infant formula feeding are modifiable if proper interventions are implemented.