This thesis on the topic of "Nondestructive Testing of Welded Joints" consists of a theoretical and an experimental part. The theoretical part of the thesis explains the methods of nondestructive testing, provides a detailed overview of their applications, and discusses their advantages and disadvantages. Special attention is given to radiographic testing due to its application in the experimental part of the thesis. The characteristic defects that may occur in welded joints and affect the strength and functionality of the components are listed. Each group of defects is described in detail, along with the causes of their occurrence. Additionally, trends in development that have brought significant transformations to the NDT field are presented, aiming to improve efficiency, accuracy, and safety. In the experimental part of the thesis, radiographic testing was conducted on a specific test plate made of structural steel S355. The testing had two objectives: to demonstrate the soundness of the weld on the test plate and to show the impact of radiation energy and film type on the quality of the radiogram. The procedure for radiographic testing is described in detail, and an analysis of the observed irregularities is provided based on the developed radiograms. The analysis of the radiograms determined that the detected irregularities in the weld affect its quality and functionality.