Electrochemical lithium intercalation into 1T-NbTe2 takes place by progressive filling of the distorted octahedral sites in the interlayer space leading to an increase in the c(m) parameter. The monoclinic structure and niobium ribbon chain modulation are preserved during lithium intercalation. On the contrary, different modulated structures are observed in the products of sodium intercalation. For Na0.6NbTe2, a a27(1/2) x a27(1/2) superlattice and a basal spacing of 9.89 angstrom are observed. The geometric relationships between ribbon chain and 3a X 3a modulations in 1T-transition metal dichalcogenides are consistent with a trimerization of 3a3(1/2) x a modulations due to the changes in the d-band electron count and metal-metal bonding with intercalation. For NaNbTe2, a fully intercalated phase with basal spacing of 8.04 angstrom and sodium ions in trigonal prismatic coordination is observed. The differences in bond ionicity for Li and Na account for these effects.