Background Long acting reversible contraceptive methods are highly effective, safe and provide uninterrupted protection to women for 3 to 12 years, yet are little used in the Ethiopia. Assessment of the utilization and predictors of long acting reversible contraceptive methods assist health planners to prioritize promotion strategies, and is a fundamental step for intervention. Therefore, this study aimed to assess the utilization and predictors of long acting reversible contraceptives among reproductive age women in Hawassa city, South Ethiopia; 2019. Methods A community-based cross-sectional study was conducted using a mixed method among the sample of 660 reproductive age women in Hawassa city, South Ethiopia from January 1–30, 2019. We have used a systematic and purposive sampling technique to select the study participants. A structured interview-administrated questionnaire and focus group discussion were used to collect the data. The data were entered using Epi data version 3.1 and analyzed using SPSS version 20. Chi-square (X2) test was used to determine the overall association between explanatory and outcome variables. The variables were entered into the multivariable model using the backward stepwise regression approach. Bi-variable and multivariable logistic regression analyses were conducted. The qualitative data were analyzed using a manual thematic analysis technique. Results The overall utilization of long acting reversible contraceptive methods was 22% (95% CI = 19.50–25.50%). Among this, 17.5 and 4.5% of women utilized the implants and IUCD, respectively. Good knowledge (AOR = 4.0; 95% CI = 1.66–9.60; P = 0.001) and positive attitude (AOR = 7.9; 95% CI = 3.84–16.10; P = 0.001) of women about LARC methods were positively associated with utilization of LARC methods. The odds of utilizing LARC methods increased 8.2 times for women who have no desire to have a child (AOR = 8.2, 95% CI = 3.13–21.30) as compared to those who have the desire to have a child. The discussion of women about LARC methods with providers (AOR = 4.1; 95% CI = 1.24–5.24) and husbands (AOR = 2.7; 95% CI =1.02–7.20) were positively associated with utilization of LARC methods. These findings were supported by the individual, institutional and socio-cultural qualitative findings. Conclusions The utilization of LARC methods far below the national target (22 V 40%) in the study area. Good knowledge and positive attitude about LARC methods, no desire to have a child, discussion with husbands and providers were major predictors of the LARC methods utilization. Increasing knowledge and positive attitude of the women about LARC methods using various methods of health education should be considered.