The purpose of this study was to examine the relationship between family communication patterns, flexibility, cohesion, and assertiveness among secondary school female students in Andimeshk, Iran. The research method is correlation. The statistical population consisted of all the secondary school female students in Andimeshk, and a sample of 313 students was selected using the multistage cluster sampling method. To measure the variables, the Family Communication Patterns Questionnaire (Ritchie and Fitzpatrick, 1998), the Family Flexibility Questionnaire (Shakeri, 2003), the Family Cohesion Scale (Samani, 2002), and the Assertiveness Scale (Ritchie and Gambrill, 1966) were employed. Pearson correlation and multiple regression were used to analyze the data. The results of Pearson correlation coefficient indicated that there is a significant relationship between communication patterns, flexibility, family cohesion, and female students' assertiveness (P<0. 001). Also, the results of multiple regression revealed that communication patterns, flexibility, and family cohesion explain 62 percent of assertiveness variance. The findings of this study show the importance of communication patterns, flexibility, and family cohesion among students. Therefore, planning of further studies is recommended in order to better understand such factors and promote the process of education and training among students.