The effect of ultrasound (US) applied before (US + i) and after (i + US) inoculation of yoghurt starter into cows' milk on some parameters of yoghurt was investigated. Lightness (L*) values, amounts of acetaldehyde, diacetyl, acetoin, ethanol, lactic, pyruvic, and acetic acid were higher in the US‐treated groups compared with control (P < 0.05). In the US + i group, the total amount of ketones increased. Lactobacillus and Streptococcus spp. numbers reached log ≥7.0 cfu/g in all groups (P > 0.05). It can be concluded that low‐intensity ultrasound applied to cows' milk before or after inoculation of yoghurt starters increases the aroma components and organic acid content of yoghurt.