Lithium and potassium–lithium tetraborate glasses doped with Cu (Li 2 B 4 O 7 :Cu and KLiB 4 O 7 :Cu) of high optical quality were obtained from polycrystalline compounds by fast cooling of the corresponding melt. Cu impurity was added to the Li 2 B 4 O 7 and KLiB 4 O 7 compounds in the form of a CuO oxide in the amounts of 0.4 and 1.6mol.%. On the basis of EPR and optical spectroscopy (absorption, emission and luminescence excitation and kinetics) data analysis it was shown that the Cu impurity was incorporated into the tetraborate glass network as Cu 2+ (3d 9 ) and Cu + (3d 10 ) ions. The EPR spectra of Cu 2+ centers were almost identical in glasses with the Li 2 B 4 O 7 :Cu and KLiB 4 O 7 :Cu compositions and were characteristic for glassy compounds. The Cu 2+ EPR spectra parameters (g-values, hyperfine constants and peak-to-peak linewidths) in the Li 2 B 4 O 7 :Cu and KLiB 4 O 7 :Cu glasses were obtained at T=300K. The characteristic broad absorption band peaked near 750nm was assigned to the 2 B 1g → 2 B 2g transition of the Cu 2+ centers. An intense absorption in the UV region (λ<350nm) was related to the Cu 2 + →O 2− charge-transfer band. Broad emission bands with the maxima near 420 and 465nm were observed in the luminescence spectra of the Li 2 B 4 O 7 :Cu and KLiB 4 O 7 :Cu glasses. The emission bands, peaked near 420 and 465nm, were characterized by single exponential decay with lifetimes τ=23 and 27μs, respectively for the Li 2 B 4 O 7 :Cu and KLiB 4 O 7 :Cu glasses (Cu content—1.6mol.%) at T=300K. Both emission bands belonged to the Cu + centers with different local environments or their distortion. A possible local structure for two types of Cu + centers in a tetraborate glass network is discussed.