Abstract: Combined effects of temperature, relative humidity and litter pH in the presence or absence of organic matter on the survival of S. typhimurium over time was studied. The litter (L: 30 cm x W: 25 cm x D: 6 cm aluminum trays filled with wood shavings) was inoculated with S. typhimurium at initial concentration of 4.8 x 107CFU/ml, then litter trays were placed in a room with microclimate similar to that of a naturally ventilated poultry house. The periodical measurement of S. typhimurium population in poultry litter in relation to the ambient environmental conditions revealed that: in the absence of organic matter; there was a non-significant (p<0.99) negative correlation (-0.07 at confidence level 95%) between ambient temperature and survival of S. typhimurium, a non-significant (p<0.53) positive correlation (+0.04 at confidence level 95%) between relative humidity and survival of S. typhimurium population and a highly significant (p<0.005) positive correlation (+0.67 at confidence level 95%) between litter pH and survival. In the presence of organic matter, there was a non-significant (p<0.55) negative correlation (-0.22 at confidence level 95%) between ambient temperature and survival, a highly significant (p<0.0001) negative correlation (-0.12 at confidence level 95%) between relative humidity and survival and a significant (p<0.05) positive correlation (+0.48 at confidence level 95%) between litter pH and survival. The study suggested that increased litter pH and relative humidity rather than temperature presented a great influence on the increased survival of S. typhimurium. New management practice that will reduce litter pH and relative humidity should be considered in the control plans of Salmonellosis in poultry farms.