The aim of this work was to study the energy transfer mechanisms from the ligand to the central lanthanide ion of tetracycline–europium (Tc–Eu) complex. The absorption spectra of a EuCl 3 .H 2 O solution was measured and absorption cross-section of Eu 3+ was estimated. The observed overlap predicts a resonant energy transfer from Tetracycline to Eu 3+ . The microscopic parameter of energy transfer was obtained using the overlap integral calculation considering a dipole–dipole energy transfer mechanism and results were compared considering an energy transfer by exchange.In this work, we report also the optical properties of Tc–Eu complex when urea hydrogen peroxide is added to the aqueous solution.