Pronunciation skills are a key feature in overall oral communication skills. Without adequate pronunciation skills language learners might be misunderstood in communicative situations. This cross-sectional study focused on learning vowel duration and quality in L2 English. The subjects were advanced Finnish learners of English, whose production was compared to a native group before and after teaching. Our results suggest that explicit pronunciation teaching made the subjects’ pronunciation of L2 vowel qualities more native-like. Both of our subject groups mastered vowel duration on a native level, which suggests that learners who are used to different degrees of vowel duration in their L1 can transfer those features into L2 even if they are used functionally differently. Our study suggests that vowel duration is easier than vowel quality for Finnish learners of English. The study also showed the positive effect of pronunciation teaching for advanced learners.