<b>Introduction:</b> Pregnancies that occur during the first year postpartum are more likely to be unplanned. This leads to an increased risk of adverse maternal and perinatal outcomes. However, modern contraceptive use during this period helps to reduce unplanned pregnancies and its associated adverse outcomes. There is scant data on postpartum contraceptives in pastoral communities in Tanzania. This study aimed to assess awareness and factors associated with postpartum modern contraceptives use among women of reproductive age in Bukombe District, Geita Region. <b>Method: </b>A community based cross-sectional study was conducted in a predominant pastoral community of Bukombe district in Geita region in north-western Tanzania from May-June 2018. A total of 511 postpartum women who were in their first year after child birth were studied. A multistage sampling technique was used to select study participants. Data analysis was performed using SPSS version 21. Multivariable logistic regression analysis was used to determine independent predictors of postpartum modern contraceptive use. <b>Results: </b>Most (97.3%) of the participants were aware about modern contraceptives. The prevalence of postpartum modern contraceptive use was 11.9%. The most frequent used contraceptive method was Implant 6.5%. Majority (75%) of women started to use the contraceptive at the first three months after delivery. Living in urban (AOR = 1.84, 95% CI: 1.20 - 3.79), business women’s (AOR = 2.34, 95% CI: 1.31 - 2.28), having last born aged 3 - 4 months (AOR = 3.30, 95% CI: 1.11 - 9.85) and menses resumption (AOR = 9.23, 95% CI: 3.60 - 23.72) were associated with postpartum modern contraceptive use. Fear of side effects, poor knowledge about contraceptives, husband restrictions, distance to health facility and availability of contraceptive were the barriers for use of contraceptive use. <b>Conclusion:</b> We found low uptake of postpartum modern contraceptive use in this population. Numerous factors were associated with modern contrac