In this study ferromagnetic shape memory alloys (Ni 47 Mn 40 ) 1-x Sn 13 Co x at (x=0.0, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.10) and Ni 47 Mn 40 Sn 13+x with x=0, 0.5, 1 synthesized by mechanical alloying technique. At first 10 grams of powders was milled at high-energy ball milling for 30 hours in an argon atmosphere. Samples were packed and sealed in the quartz tube in high vacuum and subjected to heat treatment at 950 C for 16 h. X-ray diffraction pattern demonstrated that these samples were single phase and had the high atomic ordering of L21 structure. Structural phase transition observed for all samples by AC susceptibility measurements. In Co doped samples, structural transition temperature decreases up to x=0.04 and then increases for x=0.05. With futher amount of Co (x=0.06, 0.08, 0.10) structural transition temperature decreases that is expected because of change in the lattice parameter and electron concentration (e/a) values. The structural transition were observed in Ni 47 Mn 40 Sn 13+x alloys. With excess Sn doping, the martensitic transformation (MT) temperature decreased, which can be attributed to the increase in the lattice parameter and decrease of e/a. The dynamic behavior of the alloys showed that (Ni 47 Mn 40 ) 1-x Sn 13 Co x samples with x=0.0, 0.02, 0.05, 0.06 and Ni 47 Mn 40 Sn 13+x samples with x=0, 0.5, 1 have cluster spin glass. Martensitic transformation (MT) temperatures were observed in the electrical resistivity measurements which is in agreement with the susceptibility results.