Swahili is an increasingly important language in China with its utility in the Belt and Road Initiative. A number of previous studies in third language acquisition (TLA) applied the concept of crosslinguistic influence (CLI), but there are scant studies focusing on the possible phonetic CLI in the phonetic acquisition of Swahili. The present study investigates possible phonetic CLI from Mandarin as L1 and English as L2 on L3 Swahili. Participants were 35 Swahili learners possessing the target language sequence. In this study, a 26-item questionnaire is used to collect data. The main findings of this research include the acquisition of Swahili nasal plosive consonants blocked by Mandarin and English for different reasons such as CLI source deficiency from Mandarin and negative transfer from similar consonant clusters in English. In addition, the results show that phonetic CLI is greatly caused by English for its similar “nasal stops+plosive” consonant clusters. The findings can fill the research gap of Swahili TLA field and Swahili learners with a deeper understanding of acquiring Swahili nasal plosive consonants.