Women must be aware of the risk factors of pregnancy complications and the negative maternal and fetal health consequences to take preventative measures and management strategies that will result in a successful pregnancy. This study aimed to assess the Level of Knowledge about obstetric warning signs and the associated factors among pregnant Saudi women attending antenatal care in a tertiary care maternity set-up in Riyadh City. Data for this cross-sectional study were obtained using a structured questionnaire from eligible pregnant women admitted to King Saud Medical City (KSMC) between August 2020 and March 2021. Data were analyzed using descriptive and inferential statistics. Out of a minimum estimated sample size of 170, researchers recruited 362 participants. As observed, only 92 people, or 25.4%, had enough knowledge about various educational levels. The majority (91.2%) lived in villages, had no history of chronic disease (74.0%), and said that it took them at least 30 minutes to commute from their home to the hospital (69.3%). Two hundred two (55.7%) lacked appropriate knowledge, although most women (76.2%) had one to four pregnancies. Poor psychological health resulted from 37 people's (10.2%) inadequate Awareness. Even though 139 (38.4%) had spent more than 15 minutes receiving education from medical staff and 200 (61.5%) had attended the prenatal care clinic more than four times, most lacked adequate knowledge. The variables education level (P=0.000), working status (P=0.022), and place of residence (P=0.044) showed a statistically significant association with the knowledge level, also only education level statistically significantly affected the likelihood of knowledge gaps. In conclusion, early identification of obstetric warning signs and associated risk factors of pregnancy complications is integral to prevention.