Four brands of yogurt sold by street vendors in Onitsha Metropolis, Anambra State, Eastern Nigeriia were sampled, the pH was determined and microbiological assessments were conducted in order to ascertain the total heterotrophic bacteria, coliforms and yeast in the samples (A – D) during a seven day period. The results revealed that values of pH monitored varied from 3.69 – 4.50 while a total of five bacteria species belonging to Escherichia coli, Staphylococcus aureus, Streptococcus, Lactobacillus and Bacillus species, and three fungi species belonging to Aspergillus, Rhizopus and Saccharomyces were isolated from the samples. Sample B had the highest mean heterotrophic bacteria count with a value of 6.1 x 105 cfu/ml. Statistical analysis of heterotrophic bacteria count among the 4 sample groups had p-value =0.0000374. There is a significant difference in the heterotrophic bacteria count among the groups. Low titre values of starter cultures were recorded in the control samples. Escherichia coli, an indicator of coliform was detected in all the samples and the value of 4.4 x 105 cfu/ml was observed in sample B. Coliforms, S. aureus, Bacillus species and fungi were not detected from control samples purchased directly from the producing companies. Statistical analysis of coliform count in the four groups had p-value=0.529296. There was no significant difference in the coliform count among the 4 sample groups at α =0.05 and p-value =0.529296. The findings suggest that the yogurt traded by street vendors in Onitsha Metropolis has poor microbiological quality control. This poses danger to public health. Therefore, attention of the appropriate government agencies and manufacturers is needed to ensure that sale of yogurt by vendors is done in most appropriate condition and in a mobile refrigerator to maintain adequate temperature, thereby, reduce contamination.