Milk spoilage is a problem in different parts of Tanzania especially in areas with limited cooling storage facilities, poor hygiene and lack of preservatives. On the other hand, spices and herbs which are primarily used to impart flavour and aroma in food, contain essential oils with antimicrobial activity against wide range of food spoilage bacteria. The main objective of this study was to assess the antimicrobial activity of essential oils from the most commonly used spices and herbs in Zanzibar against milk spoilage bacteria. Questionnaires, focus group discussions (FGDs) and direct observations were used to assess the knowledge on the spices and herbs added in milk at the households’ level. Steam distillation using a Clevenger system was used to extract essential oils from spices and herbs. The extracts were screened for antimicrobial activity and subsequently, minimum inhibitory concentrations (MICs) were determined by microdilution method. Results demonstrated that 96.4% (P < 0.05) of the respondents use spices and herbs in milk to add flavour, colour and for other uses such as traditional medicine. The most commonly used spices and herbs added in milk are cardamom, cinnamon, ginger and lemon grass (P<0.05). All the extracts demonstrated antimicrobial activity against Streptococcus thermophillus, Lactobacillus plantarum and Escherichia coli. The MICs ranged between 0.0039 and 0.1250 μg/μl. However there was no significant difference (P > 0.05) among all the extracts against the tested microbial strains. Further studies are recommended on other spices and herbs to investigate whether the inhibitory activities are due to bactericidal or bacteriostatic properties. Moreover, this study opens the avenue for possibilities of using essential oils from spices and herbs as a means of milk preservation and hence to overcome the income loss and food insecurity caused by milk loss through spoilage microorganisms.