The effect of exposure of Salmonella Typhimurium to guava extracts on bacterial heat resistance was investigated. After exposure to guava extracts for 3 h, the heat resistance of S. Typhimurium was determined at $57^{circ}C$. Exposure of cells to guava extracts decreased D-values in the range of 18% to 52%, compared with unexposed cells. The lowest D-value was observed in cell exposed to acetone extracts of guava fruits. Exposure to guava extracts can make cells more sensitive to heat treatment.