The promotion of rational use of antibiotics among pregnant women is eminent not only for the risk of teratogenicity in the developing fetus but also the risk of drug resistance with its concomitant high cost of health care. Studies on antibiotic self-medication among pregnant women in Northern Ghana are rare. Improving the knowledge and awareness among the vulnerable groups about the appropriate use of antibiotics can help in limiting the antibiotic resistance menace. We, therefore, conducted this study to assess the knowledge, attitude, and practice (KAP) toward antibiotic use among pregnant women attending an antenatal clinic at a primary health care in Tolon, Northern Region, Ghana. We conducted a cross-sectional study using an interviewer-administered questionnaire to assess the KAP of 702 pregnant women on antibiotic use. This study was conducted in the Tolon Health Center (THC) from March 2021 and ended in October 2021. In this study, 55.6% of pregnant women had good knowledge and 45.3% of them had engaged in self-medication with antibiotics while pregnant. There were statistically significant associations between participants' background and obstetric characteristics and knowledge of antibiotic use and antibiotic resistance, except for age, marital status, and parity. Also, there was a significant association between pregnant women's knowledge and self-medication or over-the-counter purchase of antibiotics. We concluded that higher education level, monthly income, good practice, and good knowledge were significantly associated with a reduced likelihood of self-medication with antibiotics. A well-structured education that could be easily accepted and understood by pregnant women on the risks of antibiotic self-medication should be included in the routine education at the antenatal clinics.