Connections in engineering structures such as aircraft, marine and automotive should be designed to fulfill the intended level of safety, serviceability, durability, and the ability to withstand the stresses applied on global structures. Most structures use a single connecting method such as mechanical fasteners (bolt- rivets), bonding and welding to make the connection between adjoining members. However, it is sometimes necessary to mix different joining methods in a single connection, or to replace some joints by higher strength joining elements in order to increase the capacity of an existing joint. To enable mixed joints between mechanical fasteners and welds to become a strengthening viable joining technology in industry, the present study aims to develop a better understanding for mechanical behavior of mixed joints of an overlap steel plates experimentally using the static tension test and with finite element method, either connected with single or mixed joining elements. The investigation includes a basic single joint of double fillet welds steel lap plates. Four mixed joining methods are evaluated including a combination of the basic single joint with a rivet, a bolt, an arc spot penetrate weld and a plug weld. Experimental results for static tension tests conducted at room temperature are presented and considered to be the most reliable datum line. Mixed joining techniques resulted in strengthening the basic steel structure lap joint. Also, the finite element model(FEM) which is time consuming but inexpensive was carried out to predict detailed stress-extension distributions within these joints and also to predict tensile behavior of the basic purely single joint and when mixing with other joining configurations. A comparison of finite element analysis is conducted with experimental results and the results are validated. Finite element models showed a good agreement with the experimental results. Therefore, the models procedures seem adequate for assessing stress level for use in evaluating both single and mixed joints