This study was conducted in order to prolong the period of validity of yoghurt by adding probiotics consisted of Lactobacillus acidophilus LA-5 and Bifidobacterium animalis subsp lactis (Bb12) to milk allocated to yoghurt industry and studied the microbial, chemical and sensory characteristics of yoghurt during storage periods for 0, 7،,14, 21, 28, 35 and 42 days at 4 ± 1 °C and 10 ± 1 °C. The results of microbial characteristics showed that the vital force of the first starter lasted for 7 days in the control samples while lasted for 35 days for the sample containing Lactobacillus acidophilus LA-5 or Bifidobacterium animalis subsp lactis (Bb12) when stored at 4 ± 1°C. Adding probiotics did not affect the taste, smell and pH of the yoghurt without change in the property values during storage periods. It was also found that the shelf – life of control samples can be prolonged and consumed safely up to 7 days of storage while it was prolonged for 35 days in yoghurt samples containing probiotics.