Objectives: The utilization of long-acting reversible contraceptive methods is one of the key factors in protecting women and couples against unwanted pregnancies. The study aimed to assess the determinants of long-acting reversible contraceptive use among women in Northwest Ethiopia. Methods: A community-based unmatched case-control study was conducted from 1 February to 8 March 2017 in Northwest Ethiopia. The cases were women who used long-acting reversible contraceptive methods, and the controls were women who used short-acting contraceptives. Both of them were selected using a systematic sampling method. An interviewer-administered questionnaire was used to collect the data. Epi info and SPSS version 23 were used for data entry and analysis, respectively. Descriptive statistics and association measures were done and presented in texts, tables, and figures. Results: A total of 882 women were interviewed, with a response rate of 99.3%. Women who were between 15 and 24 years old were two times more likely to use long-acting reversible contraceptive methods than those whose age was ⩾35 (adjusted odds ratio = 2, 95% confidence interval: (1.20, 3.50)). A good level of knowledge about long-acting reversible contraceptive methods (adjusted odds ratio = 11.6, 95% confidence interval: (5.42, 24.80)), a negative attitude toward long-acting reversible contraceptive methods (adjusted odds ratio = 0.31, 95% confidence interval: (0.21, 0.46)), membership in the health development army (adjusted odds ratio = 2.8, 95% confidence interval: (2.12, 3.78)), no discussion with a partner about long-acting reversible contraceptive methods (adjusted odds ratio = 2.3, 95% confidence interval: (1.54, 3.49)), and more than 2 years of desire to wait before another pregnancy (adjusted odds ratio = 23.7, 95% confidence interval: (11.63, 48.55)) were determinants of long-acting reversible contraceptive methods use. Conclusion: This study revealed that attitude toward long-acting reversible contraceptive method use, being a member of the women’s health development army, and the desire to space children were determinants of long-acting reversible contraceptive method use. More actions should be taken to increase the utilization of long-acting reversible contraceptive methods by promoting discussion between partners about modern contraceptives and increasing women’s participation in being a member of the health development army.