We report an experimental study that demonstrates control of the anchoring of a nematic liquid crystal (LC), 4'-pentyl-4-cyanobiphenyl (5CB), at an aqueous-LC interface by the reversible adsorption of a redox-active surfactant, 11-(ferrocenylundecyl) trimethylammonium bromide (FTMA). Whereas the anchoring of 5CB was found to be insensitive to the oxidation state of FTMA when using aqueous solutions of FTMA, oxidation of FTMA in aqueous mixtures of cetyltrimethylammonium bromide (CTAB) and FTMA led to a near-planar-to-homeotropic transition in the orientation of 5CB. The change in orientation of 5CB was attributed to the competitive adsorption of CTAB (which causes homeotropic anchoring) and either FTMA or oxidized FTMA (both of which cause near-planar anchoring). Because oxidized FTMA is less surface active than FTMA, oxidation of FTMA in a mixture containing CTAB and FTMA leads to an increase in the surface concentration of CTAB. Reversible control of the anchoring of 5CB was achieved by sequential contact of the liquid crystal with aqueous solutions containing CTAB and FTMA and then CTAB and oxidized FTMA. The addition of chemical oxidizing or reducing agents was also observed to change the orientation of the liquid crystal. Time-dependent changes in the optical texture of 5CB were quantitatively interpreted in terms of the tilt angle of the 5CB at the aqueous-LC interface. These results suggest new principles for control of the anchoring of LCs at interfaces as well as new experimental approaches for the study of surfactant adsorption at liquid-liquid interfaces.