Background: Placenta accreta is defined as abnormal trophoblast invasion of part or all of the placenta into the myometrium of the uterine wall. Abnormal placentation includes both abnormally adherent placenta (placenta accreta) and abnormally invasive placenta (AIP – including placenta increta and placenta percreta); the term PAS encompasses the whole spectrum of the disorder. Objective: This study aimed to construct the basic criteria of both sonographic and MRI for the diagnosis of placenta accreta spectrum and figuring out the accuracy of those criteria parallel with the definition of the most peculiar features in clinical practice. Patients and methods: This was a prospective cohort study conducted from September 2017 to May 2021 among women attending Sohag University Hospital which is considered to be the largest tertiary care maternity center in Sohag Governorate. The study included 300 pregnant females with mean age of 30.58 years old. They were suspected to have placenta accreta in the routine sonographic assessment. Moreover, the mean gestational age at which diagnosis was done was 33.46 ± 2.54 weeks. Results: The sensitivities of US and MRI were 91.66% and 93.51% respectively and their Specificities were 95.83% and 96.35% respectively with statistically non-significant difference. Therefore, both ultrasonography and non-contrast MRI examinations had an equal diagnostic reliability for diagnosis of placenta accreta spectrum. Conclusion: Both modalities have nearly the same diagnostic accuracy. Ultrasonography remains the most sensitive and commonly used imaging modality for the diagnosis of placenta accreta, because it is accurate, inexpensive, non-invasive and time-saving.