This study compares the effect of different mouthwashes that have been recommended during the Coronavirus disease 2019 (COVID-19) pandemic on shear bond strength (SBS) of universal adhesive to enamel in regards to self-etch (SE) and etch-and-rinse (ER) modes. Flat enamel surfaces were obtained from 100 sound human maxillary central incisors. They were randomly allocated to five groups according to the different mouthwashes (no mouthwash/control [Ctrl], 0.2% chlorhexidine 1.5% hydrogen peroxide [H 2 O 2 ], 0.2% povidone-iodine [PVP-I], Listerine [L]), and adhesive application modes (ER and SE) (n = 10). After the application of a universal adhesive (single bond universal), composite resin (Filtek Z250) was bonded by a cylinder-shaped mold (height: 2 mm, diameter: 2.4 mm). They were subjected to SBS test using a universal testing machine (AGS-X, Shimadzu Corp.) (crosshead speed: 1 mm/min). The resin-enamel interfaces were observed with a scanning electron microscope (SEM). The semiquantitative chemical microanalyses were performed with energy-dispersive spectroscopy (EDS). The data were statistically analyzed by two-way analysis of variance and Bonferroni test (p < .05). In SE mode, Group Ctrl revealed significantly higher SBS than all mouthwash groups (p < .05). In ER mode, Group Ctrl showed significantly higher SBS than H 2 O 2 and PVP-I groups (p < .05). ER mode caused significantly higher SBS than SE mode in all mouthwash groups (p < .05). The SEM observations highlighted that Group Ctrl had a regular and intact hybrid layer with resin tag formation while the H 2 O 2 and PVP-I groups exhibited a thin hybrid layer in both modes. EDS analysis indicated that in SE mode, all mouthwash groups presented increased O content compared to Group Ctrl. H 2 O 2 and PVP-I that were suggested for preprocedural use during the COVID-19 pandemic, reduced the enamel bond strength of the universal adhesive in ER mode. K E Y W O R D S chlorhexidine, hydrogen peroxide, mouthwash, povidone-iodine, shear bond strength 1 | INTRODUCTION Coronavirus disease 2019 (COVID-19), which causes respiratory disease resulting from SARS-CoV-2 infection, has become a major global public health problem since the beginning of 2020 (Phelan, Katz, & Gostin, 2020). The literature determines an approximate incubation period of one to 14 days for SARS-CoV-2 (Chan et al., 2020). Clinical symptoms of COVID-19 may include sore throat and/or reduction/ loss of smell or taste, cough, fever, shortness of breath, and muscle pain. However, the disease can be asymptomatic but still infectious