Sweet potato, Ipomoea batatas (L.) Lam., is a major food crop in developing countries and is considered essential for the food security of low-income populations. Among the factors limiting its production is the pest Bedellia somnulentella (Zeller) (Lepidoptera: Bedelliidae), recently recorded in Brazil, and for which no chemical control methods are available. Therefore, understanding the physiological changes caused by this pest attack is important to support management strategies. The objective was to evaluate chlorophyll a fluorescence parameters in eleven sweet potato genotypes subjected or not to B. somnulentella attack. A completely randomized design (CRD) was used, consisting of eleven treatments and twenty replicates. Initial fluorescence (F₀), maximum fluorescence (Fm), maximum/minimum fluorescence (Fm/F₀), variable fluorescence/maximum fluorescence ratio (Fv/Fm), and electron transport rate (ETR) were analyzed. In most of the genotypes evaluated, a reduction in F₀ was observed under attack by B. somnulentella, indicating photosynthetic stress, except in genotypes UFVJM 08, 18 and 291. Non-injured plants presented Fv/Fm values between 0.51 and 0.75, while attacked genotypes exhibited reduced values (0.35 to 0.53). ETR was also lower in damaged plants, evidencing photosynthetic stress. The results demonstrated a negative correlation between Fm/F_0, Fv/Fm and F₀. UFVJM 08, UFVJM 18, UFVJM 291, Brazlândia branca and Rubissol genotypes exhibited greater stability, maintaining more balanced fluorescence responses under pest pressure. Physiological differences between genotypes may reflect agronomic responses in the field.