This study aimed at investigating the effect of using Gricean maxims theory program for enhancing EFL student-teachers' conversational skills. Sixty EFL student-teachers from Faculty of Education, Minia University were selected as participants of the study. The study adopted the quasi-experimental design as the sixty participants were divided into two groups, each of thirty participants. The treatment group was taught using Gricean maxims theory program while the non-treatment group was taught following the conventional instruction. The instruments of the study included a conversational skills test (pre &post), and a rubric for scoring conversational skills test. Analysis of the results revealed that the treatment group participants achieved a significantly higher level in their EFL conversational skills than those of the non-treatment group. In the light of these results, it was concluded that Gricean maxims theory program was effective in enhancing the EFL student-teachers' conversational skills.