The study aims at measuring the entrance surface dose (ESD) of the thyroid gland of infant patients undergoing anterior-posterior (AP) chest x-ray in Usmanu Danfodiyo University Teaching Hospital Sokoto (UDUTHS). The study further determines the effective dose to the thyroid on infant patients undergoing AP chest x-ray. Also, compare the entrance surface dose of infant patients obtained from the study with other similar studies and diagnostic reference levels (DRLs) recommended by the International Commission on Radiological Protection ICRP. This is a prospective cross-sectional study and the primary source of data was obtained. Pediatric patients used for the study who are referred to the radiology department for an anteroposterior chest x-ray, UDUTH, Sokoto state, Nigeria. A non-probability sampling technique was adopted for the patient who came in for a chest x-ray (AP) and as recommended by ICRP that a minimum of 10 patients should be used to determine the ESD for each projection, therefore 15 patients were adopted for this study. The result of the ESD obtained for the thyroid on infant patients undergoing chest x-ray (AP) was averaged and the mean of the ESD was 1.38 mGy. This result was compared to similar studies done within the country and outside the country and with the European Commission on radiological protection as seen in Table 6 and Figure 3. The ESD obtained in this study is much higher than those obtained in similar studies as well as the recommended Diagnostic Reference Levels (DRLs). The method adopted in the study was recommended by the international commission on radiological protection, as a result of this, comparisons were reliably made with the reference values and similar studies. The result has shown that entrance surface doses and radiation doses to the thyroid exceed the permissible value in Usmanu Danfodiyo University Teaching Hospital (UDUTH) Sokoto.