<p>Anthracnose fruit rot disease caused by <i>Colletotrichum capsici</i> (Syd.) mainly affects pepper fruit and can drastically lower yields. The disease is prevalent in regions that produce pepper globally. Fruit yield and marketability are significantly influenced by this disease. This study focuses on evaluating potash alum or alum (Potassium aluminum sulphate) and frankincense (<i>Boswellia serrate</i>) essential oil to prevent anthracnose fruit rot disease in pepper. The ability of potash alum concentrations of 2, 3, 4 and 5% (w/v) as well as frankincense essential oil concentrations of 250, 500, 750 and 1000&#xa0;µl/L to inhibit the mycelial growth of pathogen was evaluated. The study results showed that the tested treatments significantly suppressed the pathogen’s growth. Data also indicated that potash alum, particularly at 5% concentrations, completely inhibited the pathogen’s mycelial growth. Data also indicate that frankincense oil at concentration of 1000&#xa0;µl/L had the greatest effect on pathogen mycelial development. Furthermore, dipping pepper in potash alum and frankincense oil reduced the severity of the disease under in vitro conditions. At the same time, anthracnose fruit rot of pepper was significantly reduced by using these treatments in the field for fruit spraying. Both in vitro and in vivo, potash alum was found to be more effective against the disease. Moreover, pepper fruits treated with these treatments have higher levels of total phenolic contents as compared to non-treated fruits. Titratable acidity was decreased in all treated fruits as compared to non-treated ones. These treatments can be used as safe replacements for fungicides in pepper fruit treatment to prevent anthracnose disease in the field or during storage and marketing because they generally worked well against the pathogen.</p>