ABSTRACT: BACKGROUND:Though long-acting reversible contraceptives (LARCs) are highly effective, have minimal side effects, require minimal follow-up, and are low cost, only 10% of contraceptives used in Ethiopia are LARCs. The reason for this low uptake is not understood at the country or regional level. Therefore, this study identified determinants of LARC utilization in Northwest Ethiopia. METHODS:A facility-based unmatched case control study, using LARC users as cases and short- acting reversible contraception (SARC) users as controls, had been conducted at fourteen public health institutions in Northwest Ethiopia. A systematic random sampling technique was used to select participants with a 1:2 case to control ratio (n = 1167). Binary logistic regression analysis was used to identify determinants of LARC utilization among family planning service users. RESULTS:Wealth status [AOR:1.87, 95%CI (1.08, 3.24)], history of abortion [AOR:2.69, 95%CI (1.41, 5.12)], limiting family size [AOR: 2.38, 95%CI (1.01, 5.62)], good knowledge about LARCs [AOR: 2.52, 95%CI (1.17, 5.41)], method convenience [AOR: 0.23, 95%CI (0.16, 0.34)], good availability of method [AOR:0.10 (0.05, 0.19)], less frequent visits to health facility [AOR:2.95, 95% CI(1.89, 4.62)], health care providers advice [AOR:10.69, 95%CI (3.27, 34.87)], partner approval [AOR:0.66, 95%CI (0.45, 0.97)], and favorable attitude towards LARCs [AOR:13.0, 95%CI (8.60, 19.72)] were significantly associated with LARC utilization. CONCLUSION:Professional support, favorable attitude towards LARC use, high economic status, history of abortion, advantage of less frequent visits, having good knowledge towards LARC and interest of limiting births were significantly associated with LARC Utilization. On the other hand, perceived method convenience, and contraception availability were inversely associated with it. Family planning education about the benefits of LARC should be done by health providers and media. Male involvement in the counselling and decision making about the advantage of using LARC may improve the negative influence of partners on LARC utilization. It is also recommended that, future qualitative research further explore perceptions of LARC use.