The local structure of an ion-conducting glass with nominal composition 50B2O3−10PbO−40LiF has been investigated by complementary 7Li, 11B, 19F, and 207Pb single- and double-resonance experiments. The results give insight into the structural role of the lithium fluoride additive in borate glasses: (1) LiF is seen to actively participate in the network transformation process contributing to the conversion of three- into four-coordinate boron units, as shown by 11B single-resonance as well as by 11B{19F} and 19F{11B} double-resonance experiments. (2) 19F signal quantification experiments suggest substantial fluoride loss, presumably caused by formation of volatile BF3. A part of the fluoride remains in the dopant role, possibly in the form of small LiF-like cluster domains, which serve as a mobile ion supply. (3) The extent of lithium−fluorine and lead−fluorine interactions has been characterized by 7Li{19F} and 207Pb{19F} REDOR and SEDOR experiments. On the basis of these results, a quantitative structural description of this system has been developed.