This study examined the intra-sentential patterns of code mixing in the speech of Yemeni Arabic-English speaking children in the light of Scotton (1993) and Muysken (2000). Data was drawn from the speech of four typically developing Yemeni Arabic-English bilingual children. Their ages were between six and nine years at the time of recording the data. The participants were divided into two groups: Group 1 (whose age was above 8 years) and Group 2 (whose age was below 8 years) so as to compare and contrast the results. The speech of the participants was recorded for 8 hours; 4 hours in English and 4 hours in Arabic. The participants’ proficiency in English and Arabic languages was also assessed. In terms of patterns of code-mixing, this paper dived into the minute details of the grammatical categories such as tense and mood of verbs, and produced fine-grained analysis of code mixed grammatical categories of both Arabic and English. We obtained such fine-grained analysis by means of special computer programs which we developed for this purpose. Results showed varied patterns of code mixing in Arabic and English. It was revealed that Group 1 produced more code mixing in Arabic and English languages, viz. 85.71% Arabic code mixing in English and 84.16% English code mixing in Arabic. On the other hand, Group 2 of participants produced less code mixing in Arabic and English languages, viz., 25.85% English code mixing in Arabic and 14.29% Arabic code mixing in English. Top reasons for such variation include dominance, period of exposure to English, lexical gaps and speaker accommodation. Qualitatively speaking, older children mixed more closed content words rather than the open words. The findings of this paper presented a challenge to the findings of Scotton (2002) and Gamal (2007) who maintained that nouns are the most frequent mixed grammatical categories.