This study was conducted to test the hypothesis that feeding by the bean red spider mite, Tetranychus ludeni Zacher, induces significant morphological, histological, and biochemical alterations in cowpea (Vigna unguiculata) leaves. The mite infestation would damage leaf tissues and photosynthetic structures, reduce the concentrations of primary metabolites such as chlorophyll, carbohydrates, and proteins, and trigger plant stress and defence responses through increased accumulation of phenolic compounds and proline, accompanied by changes in leaf protein profiles. Morpho-histological and biochemical impacts of feeding by the bean red spider mite, Tetranychus ludeni Zacher, on detached leaves of cowpea (Vigna unguiculata) were evaluated in the laboratory at 28 ± 2°C and 75 ± 5% RH. Cultivation of mite-infested (M+) and mite-uninfested (M–) host plants was done using replicated block-design plots. Live cultures of mites at different stages were maintained in the laboratory using the leaf flotation technique. The results showed that T. ludeni colonised both surfaces of the leaf lamina of mature leaves, and petioles showed high population densities. Initial symptoms of damage were numerous white spots at feeding sites on the leaf surface. Prolonged feeding encompassed the formation of dark brown patches, crinkling, and subsequent drying and defoliation of affected leaves. Histological studies of mite-injured leaves disclosed damage to the mesophyll layer. The concentrations of chlorophyll (a and b separately) were determined using the method described by Arnon (1949). Estimation of total protein in both M+ and M– leaves was done by Lowry’s method (Lowry et al., 1951). The amount of total carbohydrates in mite-infested and uninfested cowpea leaf samples was estimated using Anthrone’s method (Hedge and Hofreiter, 1962). Total phenol content of each extract was determined using the method of Mallick and Singh (1980), and proline in cowpea leaves was assessed using the method of Bates et al. (1973). Quantitative estimation of chlorophyll (chlorophyll a - 27.51%, chlorophyll b - 38.545%, and total chlorophyll - 34.424%), total carbohydrate (3.104%), and total protein (10.928%) showed a decrease in M+ leaves, while proline (48.858%) and total phenol (18.132%) recorded an increase in mite-infested leaves. However, the protein profile of cowpea leaves revealed prominent bands in both M+ and M– host samples. The study demonstrates that mite infestation affects the plant both qualitatively and quantitatively, and feeding damage was severe, leading to loss of plant vigour.