Comprehensive epidemiological data on prevalence, trends, and determinants of the use of unskilled birth attendants (traditional birth attendants (TBAs) and other unskilled birth attendants) are essential to policy decision-makers and health practitioners, to guide efforts and resource allocation. This study investigated the prevalence, trends, and drivers of the utilization of unskilled birth attendants during democratic governance in Nigeria from 1999 to 2018. The study used the Nigeria Demographic and Health Surveys data for the years 1999 (n = 3552), 2003 (n = 6029), 2008 (n = 28,647), 2013 (n = 31,482), and 2018 (34,193). Multivariate multinomial logistic regression was used to investigate the association between socioeconomic, demographic, health-service, and community-level factors with the utilization of TBAs and other unskilled birth attendants in Nigeria. Between 1999 and 2018, the study showed that the prevalence of TBA-assisted delivery remained unchanged (20.7%; 95% CI: 18.0–23.7% in 1999 and 20.5%; 95% CI: 18.9–22.1% in 2018). The prevalence of other-unskilled-birth-attendant use declined significantly from 45.5% (95% CI: 41.1–49.7%) in 2003 to 36.2% (95% CI: 34.5–38.0%) in 2018. Higher parental education, maternal employment, belonging to rich households, higher maternal age (35–49 years), frequent antenatal care (ANC) (≥4) visits, the proximity of health facilities, and female autonomy in households were associated with lower odds of unskilled birth attendants’ utilization. Rural residence, geopolitical region, lower maternal age (15–24 years), and higher birth interval (≥2 years) were associated with higher odds of unskilled-birth-attendant-assisted deliveries. Reducing births assisted by unskilled birth attendants in Nigeria would require prioritized and scaled-up maternal health efforts that target all women, especially those from low socioeconomic backgrounds, those who do not attend antenatal care, and/or those who reside in rural areas.