In order to stabilize the superconducting phase of the copper oxide based materials, elemental substitution method has been widely employed. The TlSr2CaCu2O7 (1212 type phase) in pure form has superconducting transition temperature (Tc) range from 0–80 K [1]. However, this phase is not easily prepared in pure form. Partial substitutions by other elements at various metal sites in this system can stabilize the 1212 phase and improve its superconducting properties [2–4]. In particular, single elemental substitution showed Tc of 80–90 K [2–6] and double elemental substitution is necessary to enhance Tc to above 100 K [7–10]. Only for Cr that a single substitution gives Tc above 100 K [11]. Cr substitution effectively replaces Tl between 10–20% to give the highest transition temperature up to 110 K [12]. The average valence of Cr in this superconductor is reported to be higher than +3. It has also been reported that in this material the Ca site can be partially occupied by Tl [12]. Local ordering of the chromate groups in this material has also been reported [13]. It is interesting to investigate further the effect of Cr substitution together with other elements on the superconductivity and formation of the 1212 phase. It is well known that most rare-earths are effective in stabilizing the 1212 phase. It is worthwhile to investigate the effect of elements other than the rare-earths, for example the transition metals, in the formation of the 1212 phase. In this letter we report the effect of partial substitution of Zn and Mn in (Tl,Cr)Sr2CaCu2O7. Mn substitution is of particular interest because it is multivalent (+2/+3/+4/+7). If Zn and Mn are in the +2 state, then there will be no change in the carrier concentration and the variation in Tc can be due to the change in volume fraction of the 1212 phase as a result of the substitution. If they exist in valence states other than +2, the variation in Tc may be due among others, to both the changes in volume fraction as well as the carrier concentration. Both elements may effect the bonding environment between the structural blocks of the thallium cuprates where lattice mismatch may occur. Samples with nominal starting composition (Tl0.85Cr0.15)Sr2(Ca1−x Mx )Cu2O7 with M=Zn and Mn were prepared via the solid state reaction using high purity oxide component (>99.99%) through the precursor method. Appropriate amounts of Sr2CO3, CaO, CuO and ZnO or MnO were mixed, ground and heated at