In this study, the synthesis of nano-structured CuNiCoZnAl high entropy alloy was performed by Mechanical Alloying (MA), and the bulk samples of this alloy was successfully prepared by Spark Plasma Sintering (). Further, the possibility of its joining was investigated by two different methods. At first, it was performed by Gas Tungsten Arc Welding (GTAW) in two ways : using filler metals and without using it and also joining by Transient Liquid Phase (TLP) method in two ways: using AWS BNi2 interlayer and copper foil interlayer. According to the results of X-ray diffraction that was carried out on the powder of this alloy during different milling times, in this alloy the solid solution was formed after 30 hours of milling with a single-phase FCC structure. This process continued to 60 hours to completing the solution of the elements in each other. The Scanning Electron Microscopy (SEM) images of CuNiCoZnAl bulk sample that was prepared by spark plasma sintering method, were confirmed the absence of any porosity and the completion of solution of the elements in each other and formation of a solid solution structure in the alloy. Also, with the help of the results of the X-ray diffraction spectroscopy of this alloy, the absence of any impurities, as well as match of the chemical composition of the alloy with the nominal compound were confirmed. According to the results of the Vickers micro hardness test, this alloy had a mean hardness value of 543 HV. Investigating the possibility of the joining of this alloy was performed by GTAW and TLP methods. In the GTAW method in both ways (using the filler metal and without using it), many problems such as : the formation of hot cracking defect, lack of fusion defect, spattering of molten metal on the tungsten electrode and on the base metal were observed. The creating of these defects can be due to the high input heat in the fusion welding method, the high vapor pressure of Zn and the low melting point of it compared to the other elements in the alloy system and high percentage of these elements. Finally, it was possible to join this alloy by the transient liquid phase using two different interlayers : AWS-BNi2 and copper foil. At the first way that was carried out by using the AWS-BNi2 interlayer, at 15, 30, 45 and 60 minutes at a temperature of 1100° C were not joined (except for 30 minutes), due to the formation of inter metallic compounds. Subsequently, this method was performed by using the copper interlayer at 15, 30 and 45 minutes. The retention time of 15 minutes at 1100° C was insufficient to make the joining in this alloy and the lack of melt volume at the bonding region resulted in the separation of two pieces from each other. By increasing the storage time to 30 and 45 minutes, the joining of the CuNiCoZnAl alloy was successfully performed. According to the images obtained from the Optical Microscope (OM) and the scanning electron microscope, the joining region at 30 minutes was mainly solidified as Athermal Solidification (AS), since the time needed to complete Isothermal Solidification (IS) was not enough. However, with increasing storage time from 30 to 45 minutes, the isothermal solidification process was performed completely and the eutectic solidification in the junction was not observed. The results of Vickers micro hardness tests around the bonding site at both 30 and 45 minutes showed that the hardness values of the second sample (storage time of 45 minutes), were more uniform and less than the first sample (storage time of 30 minutes). That is due to the disappearance of eutectic structures and completion of the isothermal solidification process at the higher storage times. The results of the shear strength tests of the joints at both 30 and 45 minutes showed that, with increasing bonding time from 30 to 45 minutes, the bonding strength increased from 73 MPa to 157 MPa. The reason for this increasing is that, as the storage time increases, the bond strength increases due to the reduction in the amount of the brittle eutectic phases. Key words: high entropy alloy, CuNiCoZnAl, nano-structured, mechanical alloying, welding, joining by transient liquid phase method.