The present research work 3,4-dihdroxy 5-methoxybenzaldehyde thiosemicarbazone (DHMBTSC) is proposed as a novel chromogenic organic reagent for the estimation of Cobalt (II) with specterophotometry. The novel chromogenic reagent 3,4-dihdroxy 5-methoxybenzaldehyde thiosemicarbazone (DHMBTSC) form yellowish brown coloured complexe by Cobalt (II). The colour complexe shows maximum absorption at lmax 389 nm. The beer’'s law validity range is 0.14733 to 1.4733 (μg/ml) and optimum concentration range is 0.2946 to 1.3259 (μg/ml).The molar absorptivity and sandells sensitivity of the complex was found to be 1.65x104 L.mol-1.cm-1 and 0.00357mg/cm2 respectively. The cobalt (II) forms M:L(I:I) colour complexe with DHMBTSC and stability constant of the complex was found to be. 2.41 x 106 . The first order derivative amplitude was measured at 432 nm. This proposed developed method is selective, rapid and applied for the estimation of Cobalt (II) in trace leveles in tea leaves samples.