Language abilities determine many things in life. Every human needs language abilities to survive, especially to communicate and socialize with others. Language abilities continue to develop in mid to late childhood, between the age of 6-11 years. The development of children's language abilites in middle to late childhood is not the same as children at comparatively younger age. In this context, there is a crucial development in language abilites, particularly in vocabulary, grammar, and pragmatic elements. Based on this fact, this study examines the ability of children in writing compound, complex, and compound-complex sentences. This study also shows the patterns found in all three types of sentences. The significance of this study is to contribute to the syntactic disciplines about the production of sentences in children's writing, especially in the production of compound, complex, and compound-complex sentences. The results of the analysis in this study can be used by teachers, researchers, and learners of language studies to create teaching materials and map the ability of boys and girls in producing compound, complex, and compound-complex sentences. The purpose of this research is to identify the language abilities in accordance to the production of compound, complex, and compound-complex sentences in writing among children, aged 10-11 years. This research also identifies the effects of gender on each pattern found in all three types of sentences. The production of sentences in this research is in Indonesian language. The respondents are 63 boys and 63 girls attending fifth grade of primary school with A grade accreditation in Depok City. The sources of data were obtained through direct communication techniques. The methods used in this research were mixed-methods. The data in this research were analyzed based on Kridalaksana's (1999) approach. The comparison of findings of each sentence pattern was statistically analyzed using Statistical Package for the Social Science (SPSS) software. The results of this research shows that the mean value of compound, complex, and compound-complex sentences produced by the girls is higher than the boys. The probability value in the production of those three kinds of sentences is also significant. However, gender-based differences in each pattern found in the three types of sentences have varying mean and probability values. © 2021 by Nova Science Publishers, Inc. All rights reserved.