We studied the temperature dependence on the gas phase reactions of theC_{2}(a^{3}*Π*_{u}) radical with several unsaturated hydrocarbons (C_{2}H_{4} (*k*_{1}),C_{2}H_{2} (*k*_{2}),C_{3}H_{6} (*k*_{3}), and 2-C_{4}H_{8} (*k*_{4})) by means of pulsed laser photolysis-laser induced fluorescence (PLP-LIF) technique. The bimolecular rate constants for these reactions were obtained in the temperature range of 298-673 K. The obtained kinetics data were used to derive the following Arrhenius expressions: *k*_{1}(*T*)=(4.53 ±0.05) ×10^{-11}exp[(196.41 ±5.20)/*T*], *k*_{2}(*T*)=(3.94 ±0.04) ×10^{-11}exp[(143.04 ±4.28)/*T*], *k*_{3}(*T*)=(7.96 ±0.17) ×10^{-11 }exp[(185.10 ±8.86)/*T*], and *k*_{4}(*T*)=(1.04 ±0.02) ×10^{-10}exp[(180.34 ±7.67)/*T*], where all error estimates are ±2*σ* and represent the precision of the fit. The observed bimolecular rate constants along with the negative temperature dependences of *k*(*T*) allow us to reacha conclusion that the reactions of C_{2}(a^{3}*Π*_{u}) with these unsaturated hydrocarbons in the temperature range of 298-673 K proceed via an addition mechanism.