The most common method of teaching genetics in Pakistani schools is through lecturing. This kind of teaching does not help students to gain in-depth understanding of the subject matter as a result students understand the subject matter at ‘knowledge’ level but not at ‘understanding’ and ‘application’ levels. The purpose of this action research was to improve students’ conceptual understanding of genetics by teaching it through inquiry method. Three cycles of action-research were carried out to teach five lessons over a six-week period. Each cycle consisted of two teaching lessons except the last one which consisted of one teaching lesson. A summative assessment was conducted at the end of the teaching to assess students’ learning in genetics. Data was collected at three stages of the study which included: pre-intervention, during intervention, and post intervention. In the pre-intervention (reconnaissance) stage, data was collected by using semi-structured interviews and classroom observations to explore the existing teaching learning process. During the intervention stage, the data was collected through observations and photography of teaching and aids used. In the post-intervention stage, data was collected by using the semi-structured interviews, both formal and informal talks with the research participants, and summative assessment of students. The findings from the study indicated that structured-inquiry based teaching helped students to conceptualize the genetic concepts at ‘knowledge’ level. However, they learn few genetic concepts at ‘understanding’ level. Summative test also shows that they did not demonstrate learning at the ‘application’ level. Initially, students showed difficulty in conducting and conceptualizing the inquiry activities but gradually they showed less difficulty when they become more acquainted with inquiry learning.