Background The aftermath of childbirth plays a vital role in addressing unmet family planning requirements and is instrumental in mitigating the risks associated with pregnancies that are closely spaced. Recognizing factors that indicate immediate postpartum utilization of long-acting reversible contraceptives is essential for crafting focused initiatives. This helps meet unaddressed family planning needs and contributes to the reduction of maternal and child mortality rates in the country. Therefore, this research aimed to pinpoint factors influencing the utilization of long-acting reversible contraceptives immediately after childbirth among women delivering in public health facilities in northwest Ethiopia. Methods A facility-based unmatched case-control study was carried out, involving 342 postpartum women (comprising 108 cases and 216 controls) who delivered in public health facilities in northwest Ethiopia. Data collection involved employing a structured interviewer-administered questionnaire, and binary logistic regression analysis was conducted. The statistically significant association between independent factors and the outcome variable was assessed using the adjusted odds ratio with a 95% confidence interval, considering a p-value less than 0.05. Result The educational status of women at secondary level and above (AOR=2.314, 95% CI=1.645-5.043), adherence to ANC follow-up (AOR=2.930, 95% CI=1.829-4.769), lack of desire to have a child (AOR=1.421, 95% CI=1.026-2.006), receiving counseling (AOR=3.029, 95% CI=2.085-5.988), and possessing knowledge (AOR=1.642, 95% CI=1.086-3.186) were identified as significantly correlated with immediate postpartum LARC utilization at p <0.05. Conclusion In this investigation, the utilization of immediate postpartum long-acting reversible contraceptives (LARC) was significantly linked to women’s educational attainment, attendance at antenatal care (ANC), their desire for additional children, counseling, and knowledge about immediate postpartum LARC. To promote family planning in the postnatal phase, it is recommended to prioritize maternal education, offer comprehensive counseling and health education, and enhance adherence to targeted ANC services.