Wind-induced interaction between a tuned liquid column damper (TLCD) and a structure (bridge deck) in pitching motion is investigated both theoretically and experimentally. Non-uniform. cross-sections in TLCDs are considered in general. Theoretically, the interacted equations of motion under wind excitation were derived for a single-degree-of-freedom rotational structure equipped with a TLCD based on energy principles. An addition term, which had never been revealed in existing literature, was discovered. The second part in this study was to demonstrate the existence of this additional term through experimental verification. This task was carried out by conducting large scale tests on the system of a TLCD on a rotational structure (which is a spring-constrained steel beam pivoted at mid-span) and by making comparisons between the experimental and analytical responses of the interacted structure subjected to harmonic loading. To obtain all necessary parameters for computing the analytical responses in the interaction, the individual identification of the properties of the TLCD and structure using free vibration and forced vibration techniques was also performed. Comparison results show that analytical responses with the additional term included can represent the actual interaction more closely than those without the additional term. Therefore, the inclusion of the additional term in pitching interaction equations is essential.