Environmentally responsive materials, i.e., materials that respond to changes in their environment with a change in their properties or structure, are attracting an increasing amount of interest. We recently designed and synthesized a series of cleavable multivalent lipids (CMVLn, with n = 2 to 5 the number of positive headgroup charges at full protonation) with a disulfide bond in the linker between cationic headgroup and hydrophobic tails. The self-assembled complexes of the CMVLs and DNA are a prototypical environmentally responsive material, undergoing extensive structural rearrangement when exposed to reducing agents. We investigated the structural evolution of CMVL–DNA complexes at varied complex composition, temperature and incubation time using small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). A related lipid with a stable linker, TMVL4, was used as a control. In a nonreducing environment CMVL–DNA complexes form the lamellar (LαC) phase, with DNA rods sandwiched between lipid bilayers. However, new self-assembled phases form when the disulfide linker is cleaved by dithiothreitol or the biologically relevant reducing agent glutathione. The released DNA and cleaved CMVL headgroups form a “loosely organized” phase, giving rise to a characteristic broad SAXS correlation profile. CMVLs of high headgroup charge also form condensed DNA bundles. Intriguingly, the cleaved hydrophobic tails of the CMVLs reassemble into tilted chain-ordered Lβ′ phases upon incubation at physiological temperature (37 °C), as indicated by characteristic WAXS peaks. X-ray scattering further reveals that two of the three phases (LβF, LβL, and LβI) comprised by the Lβ′ phase coexist in these samples. The described system may have applications in lipid-based nanotechnologies.